6 ounces grated cotjia cheese (or Monterey jack cheese)
Ground black pepper, to taste
Lime juice, to taste
12 cilantro sprigs for garnish
Heat a 10 inch sauté pan over medium-high heat. Add the oil to the pan, then the onions and season with a pinch of salt.
Sauté the onions over medium heat until golden brown. Add the garlic and cook until fragrant. Stir in the mushroom-beef mixture and chile powder. Sauté 2 to 3 minutes until the flavors meld and warm through. Stir in the cilantro and adjust the seasonings with salt, pepper, and lime juice. Keep warm.
To assemble: Place 1 tablespoon of shredded cabbage on a warm taco shell. Top with 2 tablespoons of mushroom and meat mixture. Top with a generous tablespoon of salsa, a slice of avocado, some cotija cheese, lime juice, and a sprig of cilantro.