1. Heat half the oil and fry the mushrooms until golden-brown and cooked through. Stir in the garlic, beans and spices and heat until warmed through and fragrant.
2. Beat the egg and yoghurt together until smooth; season with salt and pepper. Heat the rest of the oil in a clean pan. Dip the tortillas in the egg mixture, one by one, and fry over moderate heat until golden-brown on both sides and cooked but not dry; don’t be shy with the egg – you want tortilla French toast with a bit of body! If there’s any egg left, bake it in the pan and divide between the fried tortillas.
3. Top the tortillas with the mushroom-and-bean mixture, feta, avocado and spinach, and serve hot.