Balsamic Portobello Burgers with Caramelized Onions & Garlic Aioli

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Tray of Balsamic Marinated Portobello Burgers with Caramelized Onions and Garlic Aioli

Friends, behold one of the tastiest veggie burgers we’ve ever had.

If you’ve never tried a balsamic-marinated portobello mushroom, you probably haven’t lived. Not only are these veggie burgers delicious, they’re also relatively easy to make and require just 10 ingredients! Let’s do this!

Wood tray filled with ingredients for making homemade Balsamic Marinated Portobello Burgers with Caramelized Onions

These burgers get their flavor from fresh garlic, sea salt and black pepper, olive oil, balsamic vinegar, and Italian herbs like oregano and basil.

While they marinate you’ll make a simple garlic aioli with roasted garlic for a more subdued, sweet garlic flavor, which complements the burgers perfectly.

Baking pan filled with Balsamic Marinated Portobello Mushrooms topped with garlic and herbsCast-iron skillet of perfectly browned Balsamic Marinated Portobello Burgers

You can either grill your mushrooms or cook them on the stovetop — either way, they’re absolutely delicious.

And while that’s happening, you can sauté some onions until caramelized. These will be the perfect topper for the burgers.

Skillet of caramelized onions for topping our Portobello Burgers recipe

We hope you LOVE these burgers! They’re:

Hearty
Flavorful
Customizable
Simple to make
& SUPER satisfying

Pair these beauties with a side of greens like our Garlicky Kale Salad with Crispy Chickpeas. Or, go carb heavy with our Crispy Baked Matchstick Garlic Fries. You can’t go wrong either way!

Into veggie burgers? Be sure to check out our BBQ Black Bean Burger, Sweet Potato Black Bean Burger, Easy Grill-able Veggie Burgers, Sun-dried Tomato Chickpea Burgers, and Curried Quinoa Chickpea Burgers!

If you try this recipe, let us know! Leave a comment, rate it, and don’t forget to tag a photo #minimalistbaker on Instagram. Cheers, friends!

Glass of water and tray with two Balsamic Marinated Portobello Burgers with Caramelized Onions and Garlic Aioli

Balsamic Portobello Burgers with Caramelized Onions & Garlic Aioli

These 10-ingredient portobello burgers are the best mushroom burgers we've ever had! It’s the balsamic-herb marinade and homemade garlic aioli that sets them apart. Sure to please plant-based and meat eaters alike!
Author Minimalist Baker
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Tray of Balsamic Marinated Portobello Burgers topped with Caramelized Onions and Garlic Aioli
4.63 from 29 votes
Prep Time 1 hour 15 minutes
Cook Time 10 minutes
Total Time 1 hour 25 minutes
Servings 4 (Burgers)
Course Entree
Cuisine American, Vegan
Freezer Friendly No
Does it keep? 2-3 Days

Ingredients

GARLIC AIOLI

  • 1 head garlic (to roast)
  • 3/4 cup raw cashews
  • 2 cloves garlic, minced (omit for less intense garlic flavor)
  • 1 Tbsp avocado or olive oil
  • 1/3 cup water (or sub unsweetened almond milk for creamier consistency)
  • Salt + pepper (to taste)

BURGERS

  • 4 medium-large portobello mushrooms (organic when possible)
  • 3 Tbsp avocado or olive oil
  • 1/4 cup balsamic vinegar
  • 1 Tbsp Italian seasoning (dried basil + oregano)
  • 2 cloves garlic, minced (2 cloves yield ~1 Tbsp or 6 g)
  • 1 healthy pinch each salt and black pepper

CARAMELIZED ONIONS

  • 1 Tbsp avocado or olive oil
  • 1 medium white or yellow onion, peeled + sliced into 1/4-inch rings

FOR SERVING

  • 4 whole wheat hamburger buns (ensure vegan-friendly as needed // sub lettuce wraps or GF buns for gluten-free)
  • 2 ripe tomatoes, sliced (optional // organic when possible)
  • Lettuce or greens of choice (optional)

Instructions

  • Preheat oven to 400 degrees F (204 C) and cut off the very top of a head of garlic. Drizzle with a little oil, sprinkle with sea salt, and loosely wrap in foil. Set directly on an oven rack and bake for 1 hour. Let cool before use. Note: To save time, you could buy roasted garlic, or sub the head of roasted garlic for 3-4 additional cloves raw garlic and proceed as instructed.
  • In the meantime, place cashews in a bowl and cover with just boiling water. Let sit uncovered for 1 hour. Then drain and rinse thoroughly.
  • While cashews are soaking, use a damp washcloth or paper towel to clean the mushrooms by wiping away any dirt and removing the stems. Place stem side up on a rimmed baking sheet or 9x13-inch baking dish.
  • To a small mixing bowl, add avocado oil, balsamic vinegar, Italian seasoning, minced garlic, salt, and pepper. Whisk to combine, then pour over the mushrooms and use a pastry brush to distribute the marinade. Flip the mushrooms over and brush the other side, then flip back over to stem-side-up position. Set aside, uncovered at room temperature, to marinate (at least 30 minutes).
  • Add your drained, soaked cashews to a small blender. Take your roasted head of garlic and press out the softened garlic by squeezing from the base up until all of the garlic is extracted.
  • To the blender also add fresh garlic, avocado oil, water (or almond milk), and a pinch each salt and pepper. Blend on high until creamy and smooth, scraping down sides as needed. Taste and adjust seasonings as needed, adding more olive oil or water for creaminess or salt for saltiness. Transfer to a serving dish and set aside.
  • To caramelize onions, heat a large skillet over medium heat. Once hot, add 1-2 Tbsp avocado oil, the sliced onion, and a pinch of salt. Sauté, stirring frequently, until light golden brown and very soft (see photo). Remove from skillet and set aside.
  • Return the skillet to the stovetop (or heat a grill and lightly oil grilling surface). Once hot, add portobello mushrooms — only as many as will fit comfortably in the pan — and sauté for about 3-6 minutes on each side, or until the mushrooms are deep golden brown on the edges and softened/reduced in size (see photo). While cooking, brush with any leftover marinade for extra flavor.
  • At this time, prepare any serving items, such as browning hamburger buns on the skillet (or grill), slicing tomato, or chopping greens.
  • To serve, add a generous spoonful of garlic aioli to each bun and top with aioli, then tomato, lettuce (or greens), mushrooms, onions, and more aioli on top of the bun. 
  • Enjoy immediately. Store leftover mushrooms separately in the refrigerator up to 2-3 days, though best when fresh. Aioli will keep in the refrigerator for 7-10 days.

Video

Notes

*Recipe adapted from our 31 Meals Cookbook.
*Nutrition information is a rough estimate calculated with avocado oil and without optional ingredients.

Nutrition (1 of 4 servings)

Serving: 1 burgers Calories: 465 Carbohydrates: 40.6 g Protein: 13.2 g Fat: 29.6 g Saturated Fat: 4.3 g Sodium: 251 mg Potassium: 716 mg Fiber: 5.5 g Sugar: 9.1 g

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  1. Jackie says

    Amazing! Such a tasty and easy supper! The only substitution we made was that we added vegan mayo and lemon juice to the Aloli (for a little extra flavour)! All and all an amazing recipe!

    • Support @ Minimalist Baker says

      We’re so glad you enjoyed them, Jackie! Thanks so much for the lovely review!

  2. Catherine says

    I made this Aioli tonight to go with Brussels and it was delicious! I added a tsp of lemon and it was perfect…my husband who doesn’t typically like the “healthier” versions of things loved it and had no clue it wasn’t mayo based! Will be making this again soon!

  3. Rose Lilian Reid Montgomery says

    All I can say is… SOO GOOD! Loved the texture of the juicy portobello mushroom, and the flavour with the garlic mayo was delicious. Will be 100% making these again. Thanks for this fabulous recipe!

  4. Ash says

    I made this recipe for my friend and her family who are trying more vegan meals. These were devoured by all, even one who said they didn’t like mushrooms. The aioli was super flavorful, and my friend licked a spoon clean of it. I will definitely be saving this recipe for future meals.

    • Support @ Minimalist Baker says

      Hi Danielle, you could make a mayo-based sauce instead. We aren’t sure of exact measurements though. Let us know if you do some experimenting!

  5. Kim says

    Just made these for a summer in winter dinner party because sometimes you want to fake a BBQ in January. They were a HUGE hit! Paired with Udi’s GF buns and some tatertots on the side. Super easy, very yummy, light but satisfying!

  6. Kelly says

    These were fantastic!! Made them on the grill. I forgot to put the garlic in the marinade and for the aioli I used mayo and just the roasted garlic.

  7. Becca says

    Hands down one of the best things I’ve ever put in my mouth! This will be a staple for years to come. I didn’t use roasted garlic or let the cashews or mushrooms set for any longer than 10 minutes (although I’m sure it would have made it even more lovely) but it still turned out phenomenal! It was much quicker to make than I expected it to be too!

  8. Allie DiBenedetto says

    I think it would be helpful to include the exact recommended time for marinating (I was able to find my answer in the comments) as well as exact amounts for salt and pepper for those new to cooking. I did not make the cashew garlic spread, I just mixed some garlic powder into mayo instead. The marinade was fantastic. I was worried it would be too strong and “balsamicy” but it was perfect. I cooked the portobellos in a non-stick frying pan with a lid overtop. They definitely took much longer than 2-4 minutes per side to soften and shrink. I also feel like they would benefit from sitting on some type of drip tray for a few minutes before serving to let some of the juices drain out tnd make eating the burgers less messy. Overall, great experience for my first time cooking portobellos.

    • Dana @ Minimalist Baker says

      Thank you so much for sharing about your experience! Your feedback is helpful. We’ll see about clearing up the instructions!

  9. Gail says

    You set is great and I have gotten some excellent ideas from it. I have two Vegan granddaughters and bought ready made plant based protein that is similar to ground beef in presentation. I need some help with how to season this for presentation as a meatless main course dish made with veggies and a rice or mashed cauliflower. i would appreciate any help you may be able to provide.

  10. Kirstin says

    This recipe is AMAZING!! I followed the recipe exactly and yes, they were a bit saucy (my fave kind) but I smooshed the shrooms down in the pan with a potato masher (technical stuff!) to get out that extra juice and once removed from the pan added a bit more balsamic to cook off as a glaze. Divine!!!

  11. KristinD says

    This recipe is SO good and SO easy to make! It’s a little messy to eat, but so worth it. It’s become a staple in my house. I’ve also used the garlic aioli on vegan BLTs — it’s delicious!

  12. KristinD says

    These are so good! So easy and so messy (to eat), but SO GOOD! This has become a staple in my house. I’ve also used the garlic aioli on vegan BLTs — it’s delicious!

    • Support @ Minimalist Baker says

      Thanks so much for the lovely review, Kristin. We are so glad you enjoyed these! Next time, would you mind leaving a rating with your review? It’s super helpful for us and other readers. Thanks so much! Xo

  13. J & J says

    This is the best portobello sandwich recipe ever….It’s our favorite go to….and we grill (rather than bake) the portobellos after brushing them with balsamic dressing and sprinkling on Italian seasoning.

  14. Nicole says

    Yum! These were delicious.
    I roasted the mushrooms instead of frying and made the aioli by mixing roasted garlic with vegan mayo.
    So good, will be making again very soon.

  15. Jane Varley says

    This recipe was easy to make, it was easy to source the ingredients, and it was absolutely delicious. The balsamic vinegar complements the mushroom perfectly. I substituted sourdough bread for a roll but it would work with pretty much any bread you like.

  16. Anne says

    I made these for dinner tonight and it was delicious! I took a shortcut on the aioli and made it with vegan mayonnaise, lemon juice, and garlic powder. Everything tasted great, the mushrooms were very flavorful! I did cook them for a longer time, I like them well done and caramelized. Will definitely make again!

  17. Jose Rico Rico says

    Hi I have a multiple nut allergy but the only nuts I can eat are almonds and hazelnuts. Which of your recipes can be replaced with that and does this recipe work with almonds?

    • Dana @ Minimalist Baker says

      I wouldn’t be able to advise on all other recipes as each one is unique. As for this recipe I think it will work with blanched slivered almonds, though I’m not sure as we haven’t tested it! Let us know if you try it out!

  18. Megan DeShields says

    These are delicious, the flavor on the mushrooms was spot on! We’d made the aioli with sunflower seeds, adding a little water to loosen the texture and would likely reduce or eliminate the raw garlic next time – otherwise a lovely dish I’d be happy to make again.

  19. Karyn Neiman says

    Awesome! My new favorite “burger” recipe. I had some leftover aioli (too garlicky for hubby) and added it to black bean chili the next night. It was so good I’ll probably start making the aioli every time I make chili now :-D

  20. Anna says

    My husband and I loved these burgers and I thought everything came together really quickly (I prepped the marinade + roasted garlic earlier in the day). I didn’t end up adding the 2 raw garlic cloves in the aioli and found that to be the perfect touch of garlic when everything was put together. Thanks, Dana!

  21. Lynn says

    My mom and I loved this recipe. I added a bit of lemon juice to the aioli and threw the portobellos on the grill. Delicious!

  22. Elsie Clarke says

    Lovely burger recipe! I’ll invite my friends over for a snack, it looks so easy to prepare.

    In my recent trip to Portugal, I bought a delicious mango chutney from “meia duzia”… I’ll give it a try with this recipe.

    They also have other tasty jams and chutneys.

    Thanks!

  23. Sara says

    This was great! Super easy and very flavorful for so little time/effort! Re the aioli — I added 2 cloves of raw garlic bc LOVE garlic, and I was a bit worried because on its own it had a very powerful pungent garlic flavor. However combined with the mushrooms/tomato/lettuce/caramelized onions/bread – it was perfect! The second day we reheated some of the mushrooms and cut it into slices and made crostini with the aioli on the bottom of the crostini – fantastic!

  24. Pip Bayley says

    Hi Dana, have enjoyed making so many of your recipes but this one failed to excite.
    The layout of the recipe I found difficult to follow and the end result I felt did not merit the effort. I’m feeling that the marinade needed a ‘how long’ as I don’t think I left it for long enough (over an hour). Also did not like the sauce. But hey! My daughter did enjoy the mushroom burger. Thank you anyway.

    • Dana @ Minimalist Baker says

      Thanks for the feedback! I’ll revisit the recipe. Marinading for 30 minutes is sufficient in our experience. Thanks for sharing!

      • DETORE PEARL JAEL JOY says

        I have eaten this before, but only at restaurants. The restaurant’s BALSAMIC PORTOBELLO BURGERS WITH CARAMELIZED ONIONS & GARLIC AIOLI are very well. I hope my mom can make these one day. I have been looking at All Minimalist Baker Recipes for a long time, but haven’t found the one I like the most. My mom used to be gluten-free, but now she is basically vegan so she can’t eat like tons of things and that makes me said to just eat something gluten and hear mom say that she wishes she could eat that. So I am trying to make her something, but don’t know what to use. Do you think you have an idea of what I could use?

    • Erin says

      Just made these for my husband and I (both omnivores) and we LOVED them! Made a few small swaps for things I already had in my refrigerator, but aside from that I followed the recipe to a T and it was just delicious!

      • Support @ Minimalist Baker says

        Thanks so much for the lovely review, Erin. We are so glad you both enjoyed them! Next time, would you mind leaving a rating with your review? It’s super helpful for us and other readers. Thanks so much! Xo

  25. Heidi says

    This looks awesome. I like portabelka mushroom burgers and am looking forward to trying this one. Could I use roasted cashews or raw almonds instead of raw cashews for the aioli? I can not eat raw cashews.

  26. Carol Edwards says

    I love mushrooms, I love carmalized onions and I love garlic but unfortunately this recipe didn’t do it for me. It was hard to hold together in the bun and it was very wet and dripped all over. The mushrooms were hard to bite into. I still love your website though and most of your recipes are awesome.

    • Dana @ Minimalist Baker says

      Hmm, sounds like the burgers just didn’t get cooked for long enough. Not sure about the wet bun….

  27. Tanya Wadley says

    I will say that this was time-consuming the first time (making buns and a 15 minute grocery trip was part of that. But I’m making it again in a couple of days with guests and I won’t have to do the buns, marinade, or aioli again. : ) My husband raved about it.

  28. Tanya W says

    This was super delicious. I doubled the carmelized onions. I made the mistake of adding another raw clove to the aioli to make 3 cloves, when I should have decreased it to 1 instead of 2… lesson learned. I had to mix the aioli with mayonnaise for it not to be super overpowering, sharp garlic flavor. I look forward to making it again with less raw garlic. I made buns using this recipe (wheat flour and some vital wheat gluten instead of white). I had a lot of aioli left over and enough marinade to make this again in the next few days.

    Thanks!

  29. Laurie says

    The mushrooms were delicious but the aioli was bland so I added some apple cider vinegar, sriracha, and lemon zest – that really woke it up! Delicious!

  30. Kim Ansberry says

    I’m not big on hamburger buns , so we used toasted ten grain bread and it was out of this world! This will be great for lunch tomorrow. The aioli was the perfect touch. Thanks again Dana!

  31. Amy says

    Would love to give these a try, however we don’t eat vinegar of any kind. Is it possible to omit or perhaps substitute with another ingredient and still have a tasty burger?

    • Dana @ Minimalist Baker says

      Hmm, I’d say get creative and go a different route – maybe sub a bit of coconut aminos? It would provide a similar effect!

    • Dana @ Minimalist Baker says

      What about silken tofu as the base? Or hemp seeds (unsoaked) or sunflower seeds (soaked)?

    • Lauren Velasco says

      The flavors in this recipe go together perfectly. The balsamic compliments the portabello very well. I used muenster cheese and baby kale as well. I prefer this to a beef burger.