Combine the mince, mushrooms, garlic, herbs and mushrooms in a bowl and mix thoroughly. Add the breadcrumbs and season generously with salt and pepper. Set aside for 30 minutes.
Form into four patties, then fry in vegetable oil in a pan over a moderate heat for 10 minutes, turning often, until firm to touch. Place the base of the ciabatta rolls on a plate, top with salad leaves, sliced avocado and tomato, add patties, and then drizzle over pesto.