Heat a large rimmed pan over medium heat. Once hot, add oil or water and shallot and sauté for 2 minutes, stirring occasionally.
Add mushrooms and coconut aminos and increase heat to medium-high. Sauté for 5 minutes, stirring frequently. Add a pinch of salt and pepper.
Add thyme, lentils, and 2 cups (480 ml // or the smaller end of the range if adjusting recipe size) vegetable broth. Bring to a low boil over medium-high heat. Once boiling, reduce heat to a simmer and cook on low for about 20 minutes, adding more broth as needed if the mixture looks dry.
In the meantime, add potatoes to a large pot and cover with water so they are just submerged. Bring to a boil on high heat and cook for 12-15 minutes or until they slide off easily when pierced with a knife.
Once tender, drain potatoes and add back to pot or a mixing bowl. Season with salt, pepper, and a bit of olive oil and mash until tender and fluffy. For added moisture in place of oil, add unsweetened plain almond milk or vegetable broth.
Once lentils are tender, taste sauce and adjust flavor as needed, adding more salt or coconut aminos for saltiness, pepper for spice, or tomato paste for more depth of flavor (optional - we didn't find it necessary). Turn off heat and let the mixture rest so flavors can deepen. Add the 2 Tbsp (30 g // or more as needed) mashed potatoes to the lentil mushroom stew and stir in to thicken.
To serve, divide mashed potatoes between serving plates or bowls and top with desired amount of lentil and mushroom gravy. Garnish with fresh parsley, vegan parmesan cheese, or more thyme, if desired.
Store leftovers separately, covered, up to 4 days in the refrigerator or in the freezer up to 1 month. Reheat on the stovetop or in a 350 degree F (176 C) oven until hot.
*Nutrition information is a rough estimate calculated with 1 Tbsp oil and without optional ingredients. *As written, this recipe heartily serves 2 as an entrée or 4 as a side.