Preheat oven to 400 degrees F (204 C) and set out a rimmed baking sheet or a large baking dish. (Or, if grilling, heat grill.)
If you don't have any cooked quinoa on hand, start by heating a medium saucepan over medium heat. Once hot, add avocado oil or coconut oil or water (1 tsp as original recipe is written) and rinsed and drained quinoa (1/2 cup as original recipe is written). Sauté for 1-2 minutes, stirring frequently to toast. Then add 1 cup water and a pinch of salt (amounts as original recipe is written // adjust if altering batch size).
Bring to a boil over medium-high heat. Then reduce heat to simmer and cook until liquid has mostly absorbed and the quinoa is tender (~15-18 minutes). Drain off any excess liquid if needed. Then set off the heat uncovered to let any excess moisture evaporate.
In the meantime, add mushrooms to a shallow baking or serving dish and season with oil (or water or vegetable broth), balsamic vinegar, lime juice, cumin, chili powder, and sea salt. Flip/toss to combine and set aside to let marinate.
Next, prepare vegetables by heating a large skillet over medium heat. Once hot, add oil or water (1 Tbsp (15 ml) as original recipe is written // adjust if altering batch size), sweet potatoes, and bell pepper. Sauté for 3-5 minutes (covered) or until slightly browned, stirring occasionally.
Add cabbage, 1/2 tsp cumin, 1/2 tsp chili powder, and 1/4 tsp sea salt (amounts as original recipe is written // adjust if altering batch size) and sauté for another 3-5 minutes or until all vegetables (especially potato) are tender and slightly golden brown. Set aside.
Transfer vegetables from skillet to a large mixing bowl and set aside. Then, to the same skillet over medium heat, add the mushrooms and sauté for 2 minutes on both sides to brown and soften. Cover to lightly steam for the final minute. Then transfer to a baking sheet face up and set aside.
To the mixing bowl with the vegetables, add cooked quinoa, drained black beans, remaining 1/2 tsp cumin, 1/2 tsp chili powder, 1/4 tsp sea salt (amounts as original recipe is written // adjust if altering batch size), and lime juice and toss to combine.
Divide the filling between the mushrooms (some may overflow - that's fine). Bake at 400 degrees (or on the grill, covered) for about 5 minutes or until mushrooms and toppings are hot and slightly browned.
Enjoy immediately as is or with a sauce of choice (optional // I think the magic green sauce goes awesome with this recipe!). Store leftovers separate from sauce(s) and covered in the refrigerator for 3-4 days. Reheat in a 350-degree F (176 C) oven or the microwave until hot.
*To keep this recipe grain-free, omit the quinoa, double the black beans, and double the vegetables. *If you aren’t into mushrooms, you could sub eggplant (similar to this recipe) or halved bell peppers (like in this recipe). You could also use this as a taco salad topper, or enchilada stuffer (just double the amount of beans). *Cook time reflects prepping vegetables and mushrooms while quinoa is cooking. *Nutrition information is a rough estimate calculated with beans, quinoa, vegetables, and no sauce.