01 - Preheat oven to 400°F. Lightly grease a large baking dish with cooking spray or a small amount of olive oil.
02 - Place each chicken breast between two sheets of plastic wrap. Using a meat mallet or rolling pin, pound the chicken to an even ½-inch thickness for uniform cooking.
03 - Arrange three shallow bowls. Place flour in the first bowl. In the second bowl, whisk together eggs and milk until well combined. In the third bowl, combine breadcrumbs, ½ cup Parmesan cheese, oregano, garlic powder, salt, and black pepper.
04 - Dredge each chicken breast in flour, shaking off excess. Dip into the egg mixture, allowing excess to drip off. Press firmly into the breadcrumb mixture to coat thoroughly on both sides.
05 - Heat 4 tablespoons olive oil in a large skillet over medium-high heat. Fry chicken breasts for 2 to 3 minutes per side until golden brown and crispy. Transfer to a paper towel-lined plate to drain. The chicken will finish cooking in the oven.
06 - In a saucepan, heat 1 tablespoon olive oil over medium heat. Add minced garlic and sauté for 30 seconds until fragrant. Pour in marinara sauce, dried basil, and sugar if using. Simmer for 5 minutes, stirring occasionally.
07 - Spread 1 cup of sauce evenly across the bottom of the prepared baking dish. Arrange fried chicken breasts on top of the sauce. Spoon remaining sauce over each chicken piece. Sprinkle evenly with shredded mozzarella cheese and remaining ½ cup Parmesan cheese.
08 - Bake uncovered for 18 to 20 minutes, or until cheese is bubbling and lightly browned, and chicken reaches an internal temperature of 165°F when tested with a meat thermometer.
09 - Remove from oven and let rest for 5 minutes. Garnish with chopped fresh basil or parsley. Serve immediately while hot.