Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.
Place the chicken breasts between two sheets of plastic wrap or wax paper. Use a meat mallet or rolling pin to gently pound them to an even thickness of about 1 inch.
In the first shallow plate, place the flour. In the second plate, whisk the eggs until well combined. In the third plate, mix the breadcrumbs, grated Parmesan cheese, garlic powder, oregano, salt, and black pepper.
Dredge each chicken breast in flour, shaking off excess. Next, dip it into the egg mixture, allowing any excess to drip off. Finally, coat the chicken in the breadcrumb mixture, pressing gently to adhere.
Place the breaded chicken breasts on the prepared baking sheet. Spray the tops lightly with cooking spray or drizzle with olive oil for extra crispiness.
Bake in the preheated oven for 20 minutes. Then, remove the chicken from the oven, spoon marinara sauce over each piece, and sprinkle mozzarella cheese on top.
Return the baking sheet to the oven and bake for an additional 10 minutes, or until the cheese is bubbly and golden brown, and the internal temperature of the chicken reaches 165°F (75°C).
Remove from the oven and let it sit for a few minutes. Garnish with fresh basil leaves, if desired, before serving.