01 - Preheat the oven to 400°F and line a baking sheet with parchment paper or lightly grease it.
02 - Place chicken breasts between two sheets of plastic wrap and pound to an even 1/2-inch thickness.
03 - Arrange flour in the first shallow dish; whisk eggs with milk in the second; combine breadcrumbs, Parmesan, garlic powder, oregano, salt, and pepper in the third.
04 - Dredge each chicken breast in flour, shaking off excess, dip into egg mixture, then coat thoroughly with breadcrumb mixture, pressing gently to adhere.
05 - Heat olive oil in a large skillet over medium-high heat and fry chicken breasts for 3–4 minutes per side until golden brown. Transfer to the prepared baking sheet.
06 - Spoon 2–3 tablespoons of marinara sauce over each chicken breast and top evenly with shredded mozzarella cheese.
07 - Bake in the preheated oven for 15–18 minutes until cheese is melted and bubbly and chicken reaches 165°F internal temperature.
08 - Bring a large pot of salted water to a boil. Cook spaghetti according to package instructions until al dente. Drain and toss with olive oil and 1 1/2 cups marinara sauce.
09 - Serve spaghetti topped with a chicken breast and garnish with fresh basil if desired.