Preheat the oven to 350° and lightly grease a small casserole baking dish. (If doubling the recipe, use a bigger baking dish.)
Slice the chicken breasts in two, width-wise (like you would butterfly it but all the way through). Cover the cutting board with saran wrap, place the chicken halves on it and cover them with another sheet of saran wrap. Pound the chicken halves carefully, do not pound all the way thorough or break the skin. Salt and pepper the chicken.
Mix bread crumbs with dry Parmesan cheese and some salt and set aside. Mix the marinara sauce with some minced basil and set side.
Spread about 1-2 tbsp of marinara sauce over the chicken.
Slice the mozzarella cheese into thin slices and divide them between the chicken halves (about 2-3 slices per breast).
Roll up the chicken, tightly. Bread the chicken by rolling it in bread crumbs, then the whisked egg and then again in bread crumbs.
Spread the remaining marinara sauce over the bottom of the baking dish and place the chicken in the dish, seam down.
Bake for 25-30 minutes. Sprinkle the shredded Parmesan over the chicken and bake for another 5-7 minutes.
Video
Notes
Disclaimer: Nutrition information shown is not guaranteed to be 100% accurate as most ingredients and brands have a slight variation.