To prepare a vegetarian mushroom tacos recipe, you'll need: Mushrooms. You can use any type of mushroom you like, as long as it isn't white or pink in color. If you want to use white mushrooms, cook them in boiling water until they're tender, about 5 minutes. Toss the mushrooms with 1 tablespoon of olive oil and 1 teaspoon of salt. Cook the mixture over medium-high heat until it's browned on all sides. Remove the skillet from the heat and stir in 2 tablespoons of sour cream and 1/4 cup of chopped parsley. Season with salt and pepper to taste. Serve with tortilla chips.