Place your chicken breasts in-between two sheets of baking paper or cling wrap and pound with a meat mallet or rolling pin until they are about ½ inch thick all over.
Lightly oil the breasts and then grill them until they are browned all over and almost cooked. Place on a lined baking tray.
Spoon the marinara on top and spread out.
Sprinkle chopped prosciutto and thinly sliced spring onions over the top and finish with a good coating of cheese.
Pop under the broiler until the cheese is brown and bubbly. Serve with a big salad.