Preheat your oven to 400°F. Pat the chicken breasts completely dry with paper towels. If your breasts are large, pound them with a meat mallet between two sheets of plastic wrap until they are an even 1/2-inch thickness. Season both sides generously with the salt and pepper.
Set up a breading station with three shallow dishes. Place the flour in the first dish. In the second dish, whisk together the eggs and milk until smooth. In the third dish, combine the breadcrumbs and grated Parmesan cheese.
Dredge each chicken breast first in the flour, shaking off any excess. Next, dip it fully into the egg mixture, allowing the excess to drip off. Finally, press it firmly into the breadcrumb mixture, coating both sides evenly.
Heat the olive oil in a large, oven-safe skillet over medium heat. Once the oil shimmers, carefully add the breaded chicken. Cook for 3-4 minutes per side, until the coating is golden brown and crispy.
Remove the skillet from the heat. Pour the marinara sauce around the chicken in the skillet. Top each piece of chicken with slices of mozzarella cheese.
Carefully transfer the skillet to the preheated oven. Bake for 15-18 minutes, or until the cheese is completely melted and bubbly and the chicken is cooked through. Garnish with fresh basil before serving.