Blitz the bread in a food processor into bread crumbs, add the 50g finely-grated parmesan and blitz again to combine.
Pour the breadcrumbs into a large bowl.
Mix the egg and milk together in a large bowl.
Flatten the chicken breasts by placing them between 2 pieces of Clingfilm and, using a rolling pin or similar object, whack the breasts to flatten them out.
Dip each breast into the egg mixture on both sides and allow the excess to drip off before placing into the breadcrumb mixture and pressing the breadcrumbs into the chicken to ensure they are well coated.
Shallow fry the breasts in batches in a non-stick pan on medium heat until golden brown on both sides (approximately 8 minutes).
Pour half the pasta sauce into a medium-sized baking dish and top with the breasts.
Top each breast with 2 slices of mozzarella and then pour over the remaining sauce.
Sprinkle over the remaining 50g parmesan and bake in the oven for 30 minutes.