Preheat the oven to 400°F / 200°C and set up three shallow dishes with flour, beaten eggs, and a mixture of breadcrumbs and half the Parmesan cheese.
Dredge each chicken breast in flour, dip in egg, then coat thoroughly in the breadcrumb-Parmesan mixture.
Heat olive oil in a large oven-safe skillet over medium-high heat and cook the chicken for 3 to 4 minutes per side until golden brown.
Spoon marinara sauce over each chicken breast, then top with mozzarella and the remaining Parmesan cheese.
Transfer the skillet to the oven and bake for 12 to 15 minutes until the cheese is melted and bubbly and the chicken reaches 165°F / 74°C.
Rest for 3 minutes before serving to let the juices settle and the cheese set.