Open the chicken fillet to make it bigger and thinner. If necessary use a steak hammer.
Season with salt and pepper.
Spread the pesto, arrange the mozzarella cheese and close the fillet with toothpicks.
In a bowl, mix Parmesan cheese with breadcrumbs.
Baste the chicken with the egg and then the Parmesan mixture with breadcrumbs.
Transfer to a baking dish and bake at 350ºF for 20 minutes or until the chicken is cooked.