Shred drained tofu with a grater. Heat olive oil in a large skillet and add tofu, mushrooms, onions, garlic, 2 tablespoons salsa, taco seasoning, and soy sauce. Saut for about 5 minutes, until mushrooms are tender. Meanwhile, heat black beans (in the microwave or over the stove) until warm. Warm tortillas in the microwave for 1 minute.
To assemble tacos: Fill each tortilla with about 1/4 cup tofu-mushroom mixture, 1/4 cup beans, 1/4 cup lettuce, 1/4 tomato, 1 slice of avocado, 2 tablespoons cheese (if using) and 1 tablespoon salsa.
Nutritional information per serving: 244 calories, 10 g protein, 10 g fat, 2 g saturated fat, 31 g carbohydrate, 7 g fiber, 2 g sugar, 217 mg sodium.