01 - Preheat the oven to 400°F and line a baking sheet with parchment paper.
02 - In a saucepan, heat 2 tablespoons olive oil over medium heat. Add minced garlic and chopped onion; sauté for about 3 minutes until softened. Stir in crushed tomatoes, dried basil, oregano, salt, black pepper, and sugar. Simmer uncovered for 15 to 20 minutes, stirring occasionally. If desired, stir in fresh parsley. Keep warm.
03 - Pound chicken breasts to an even thickness of approximately 0.75 inch. Season both sides with salt and black pepper.
04 - Arrange three shallow bowls: place all-purpose flour in the first, beaten eggs mixed with milk in the second, and combine Italian-style breadcrumbs, 1/2 cup Parmesan cheese, garlic powder, and dried oregano in the third.
05 - Dredge each chicken breast first in flour, then dip in the egg mixture, and finally coat thoroughly with the breadcrumb mixture.
06 - Heat 1/4 cup olive oil in a large skillet over medium-high heat. Fry the breaded chicken breasts for 3 to 4 minutes per side until golden brown, but not fully cooked. Drain on paper towels.
07 - Place the fried chicken breasts on the prepared baking sheet. Spoon a generous amount of marinara sauce over each piece, then top with shredded mozzarella and the remaining 1/4 cup grated Parmesan cheese.
08 - Bake in the preheated oven for 15 to 18 minutes, or until the internal temperature reaches 165°F and the cheese is melted and bubbly.
09 - Meanwhile, bring a large pot of salted water to a boil. Cook spaghetti according to package directions until al dente. Drain well.
10 - Plate the cooked spaghetti, spoon additional marinara sauce on top, and place a chicken parmesan breast over the pasta. Garnish with fresh basil or parsley if preferred.