01 - Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper or lightly grease it.
02 - Place chicken breasts between two sheets of plastic wrap and pound to approximately 1/2-inch thickness using a meat mallet.
03 - Season both sides of the chicken breasts evenly with salt and freshly ground black pepper.
04 - Arrange three shallow bowls: one with flour, the second with whisked eggs and milk, and the third with a mixture of Italian-style breadcrumbs and 1/2 cup Parmesan cheese.
05 - Dredge each chicken breast in flour shaking off excess, dip into egg mixture, then coat thoroughly with breadcrumb and Parmesan mixture.
06 - Heat olive oil in a large skillet over medium-high heat. Fry chicken breasts in batches for 3 to 4 minutes per side until golden and crisp. Transfer to a paper towel-lined plate to drain.
07 - Cook spaghetti according to package instructions until al dente. Drain and set aside.
08 - Place fried chicken breasts on the prepared baking sheet. Spoon marinara sauce over each piece and evenly distribute mozzarella and additional Parmesan cheese on top.
09 - Bake in the preheated oven for 15 minutes or until cheese is melted, bubbly, and chicken reaches an internal temperature of 165°F (74°C).
10 - Serve chicken breasts atop spaghetti, garnished with chopped fresh basil if desired.