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 and gently pound them until they are evenly thick.
In a shallow bowl, whisk together the eggs and milk.
In another bowl, combine the breadcrumbs, Parmesan cheese, garlic powder, onion powder, Italian seasoning, salt, and black pepper.
Dip each piece of chicken into the egg mixture.
Coat the chicken completely with the breadcrumb mixture, pressing gently so the coating sticks well.
Arrange the chicken breasts on the prepared baking sheet.
Drizzle olive oil over the top of the chicken.
Bake for 20 minutes or until the coating becomes golden brown.
Remove the baking sheet from the oven and spoon marinara sauce over each piece of chicken.
Sprinkle shredded mozzarella cheese evenly over the top.
Return the chicken to the oven and bake for another 8–10 minutes until the cheese melts and the internal temperature reaches 165°F (74°C).
Turn on the broiler for 1–2 minutes if you want the cheese to become slightly golden and bubbly.
Remove the chicken from the oven and allow it to rest for 5 minutes.
Garnish with freshly chopped parsley and serve warm with pasta, garlic bread, or a fresh salad.