Line a baking tray with alfoil so that there is enough foil to totally wrap the breasts in. Preheat oven to 190 degrees C.
Slice a pocket in each chicken breast, stuff with 4 to 5 pieces of sliced pepperoni and a piece of sliced mozzarella. Place all the breasts on the foil.
Scatter the cherry tomatoes, the rest of the pepperoni and basil leaves on the top of the chicken breasts. Add some freshly ground black pepper, pour over the olive oil. seal the foil parcel and cook in the preheated oven for 45 mins.
After 45 mins undo the foil parcel and place back in oven for 10 to 15 mins.
Rest for 5 mins and serve with some warm crusty bread to mop up all the delicious juices.