Lay the slices of chicken breast between two sheets of paper and use a rolling pin to bash them a bit until they are half the thickness.
Mix the parmesan, garlic powder into the breadcrumbs then dip each chicken breast piece in flour, eggs and the bread crumb mix. Fry in the hot oil until golden brown (around 340°F/170°C for two minutes). Lay on greaseproof paper.
Place the bottom halves of the buns in a baking tray (make sure they are quite a tight fit), then lay the chicken slices on top. Smother these with the passata, grated mozzarella and parmesan then top with the other halves of the buns. Brush these with butter and then top with baking paper and squash with another tray. Bake at 360°F/180°C.