Fry mushrooms in a drizzle of olive oil until golden brown. Season with salt, pepper and taco spice. Add black beans and corn and stir together until hot and flavours have mixed. Set aside and keep warm. Scramble eggs in simmering butter until done to your liking. Season. Keep warm. Prep the rest of your taco toppings. Toast your flour tortillas over a gas burner using tongs until charred on the edges and warm throughout. If you do not have a gas hob toast the tortillas in a dry pan until warm. Assemble the tacos by layering with the scrambled eggs, mushroom, bean and corn mix, fresh avocado, tomatoes, red onion and chilli. Squeeze over some lime juice and serve.