Place the chicken breasts between clingfilm sheets, and bash out with a rolling pin until they are nice and thin.
Dip the chicken in the egg, then breadcrumbs, mixed with half the Parmesan. Set aside on a plate in the fridge while you make the sauce.
Heat the oil and cook the garlic for 1 minute, then add the tomatoes, passata and oregano before allowing to simmer for 5-10 minutes.
Heat your grill to high, and cook the chicken for 5 minutes each side, then remove.
Pour the tomato sauce into a shallow ovenproof dish and top with the chicken.
Scatter over the mozzarella and remaining Parmesan, and grill for 3-4 minutes until the cheese has melted and the sauce is bubbling.
Serve with pasta, and enjoy!