Flatten the chicken breasts to an even thickness using a meat mallet.

Set up a breading station with three shallow dishes: one with flour seasoned with salt and pepper, one with beaten eggs, and one with a mixture of breadcrumbs and Parmesan cheese.

Coat each chicken breast in flour, dip in egg, and then dredge in the breadcrumb mixture.

Heat oil in a large skillet over medium heat. Fry the chicken until golden brown and cooked through, about 4 minutes per side.

Preheat your oven to broil. Open the hoagie rolls and place them on a baking sheet.

Place a fried chicken breast on each roll and top with marinara sauce and two slices of mozzarella cheese.

Broil the sandwiches open-faced just until the cheese is bubbly and golden, about 3-4 minutes.

Close the sandwiches, slice in half, and serve hot.