Preheat your oven to 400°F (200°C).
Place the chicken breasts between two sheets of plastic wrap and gently pound them to an even thickness of about 1/2 inch.
Set up a breading station with three shallow bowls: one with the flour, one with the eggs beaten with water, and one with the breadcrumbs mixed with Parmesan cheese, garlic powder, Italian seasoning, salt, and black pepper.
Dredge each chicken breast first in the flour, shaking off excess, then dip into the egg mixture, and finally coat evenly with the breadcrumb mixture.
In a large oven-safe skillet, heat the olive oil over medium heat. Add the breaded chicken breasts and cook until golden brown on both sides, about 3 minutes per side. Remove from heat.
Spread 1/2 cup of marinara sauce evenly over the bottom of a 9×13 inch baking dish. Place the browned chicken breasts on top of the sauce.
Spoon the remaining marinara sauce evenly over the chicken breasts.
Sprinkle the shredded mozzarella cheese evenly over the sauce-covered chicken.
Cover the baking dish tightly with aluminum foil. At this point, you can refrigerate the dish for up to 24 hours to make ahead.
When ready to bake, preheat the oven to 375°F (190°C). Bake the covered chicken parmesan for 20 minutes.
Remove the foil and bake uncovered for an additional 10 minutes, or until the cheese is bubbly and golden.
Remove from the oven and let rest for 5 minutes before serving.
Garnish with chopped fresh basil leaves and serve hot.