Season the chicken breasts with 3/4 tsp salt and 1/2 tsp black pepper or to taste.
Cut a deep slit into each breast without cutting all the way through and stuff each with 2-3 Tbsp of mozzarella, closing the edges to seal.
Set up 3 large bowls. In the first, pour 1/2 cup flour. In the second, beat 2 large eggs thoroughly with a fork. In the third, stir together 1/2 cup bread crumbs and 1/3 cup parmesan cheese.
Working with 1 stuffed chicken breast at a time, carefully dredge in flour, tapping off any excess.
Then dip into the beaten eggs, letting any excess egg drip back into the bowl.
Finally dip in bread crumbs, turning a couple times to get a good coating.
Place a large, deep pan or dutch oven over medium heat and add 3 Tbsp olive oil to lightly coat the pan.
Once the oil is hot, add the breaded chicken in a single layer and sauté 4 min per side or until golden brown on each side.
Pour 2 cups marinara sauce around the chicken and spoon some of the marinara onto the center of each breast.
Sprinkle remaining mozzarella over the stuffed chicken then bake uncovered at 400˚F for 15-20 min, or until an instant read thermometer reads 165˚F when inserted into the chicken.
Garnish with freshly chopped basil.