Preheat your oven to 375 degrees Fahrenheit and prepare the chicken. Place each chicken breast between two sheets of plastic wrap and using a rolling pin, gently pound the chicken until it is about 1/2 inch thickness. Season both sides of the chicken with salt and pepper.
In a shallow dish, whisk together the egg and milk together and set aside. In a separate shallow bowl, combine the breadcrumbs, grated Parmesan cheese, and seasonings.
Dredge each chicken breast in the egg mixture, allowing any excess to drip off. Then place the chicken into the breadcrumb mixture, pressing gently to adhere the Parmesan cheese and breadcrumbs to the chicken. Place it onto a plate while you continue the process with the remaining chicken.
In your large oven-safe skillet, heat the olive oil over medium-high heat. Add your breaded chicken to the olive oil and saute the chicken for 2 minutes. Flip the chicken over and saute it for an additional 2 minutes. Place the entire skillet into the oven and cook for 20 minutes.
After 20 minutes, place about a couple of tablespoons of marinara sauce on top of all the chicken, followed by the mozzarella cheese. Place the skillet back into the oven for an additional 10 minutes so that the sauce is heated through and the cheese has melted.
Garnish with fresh basil leaves, if desired, and serve over your favorite pasta with additional marinara sauce. Enjoy!