Lay the chicken breasts on a flat surface. Slice the chicken breasts in half (horizontally to create 4 cutlets) and pound them using a meat mallot, rolling pin, a glass mason jar, or whatever you can get your hands on. You do this so the chicken cutlets are evenly sized especially in terms of thickness so they cook at a consistent temperature. 1/4 of an inch to 1/2 of an inch is ideal.
Sprinkle mozzarella cheese onto each of the chicken breasts. The amount of cheese you will need will vary based on the size of your chicken.
Roll the chicken in half (lengthwise) to seal the chicken. Secure the chicken with toothpicks. This will keep the cheese from slipping out of the chicken. This is when you can assess if you have added too much cheese or if you can stuff more into the chicken.
Set up a cooking station with 3 separate bowls large enough to dip the chicken. Add flour to one bowl and the beaten egg to another.
In the third bowl, combine the breadcrumbs, Italian Seasoning, salt, and pepper to taste in a bowl large enough to dip the chicken. Stir to combine.
Dip the chicken in the flour, then the egg, and then the breadcrumbs mixture.