Preheat the oven to 400°F (200°C).
Place the chicken breasts between two sheets of plastic wrap and pound them to an even thickness of about 1/2 inch using a meat mallet or rolling pin.
Set up a breading station with three shallow dishes: one with the flour, one with beaten eggs mixed with water, and one with the breadcrumbs, grated Parmesan cheese, garlic powder, Italian seasoning, salt, and black pepper combined.
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. Press breadcrumbs onto the chicken to adhere well.
Heat olive oil in a large skillet over medium heat. Add the breaded chicken breasts and cook for 3-4 minutes per side until golden brown but not cooked through. Remove from heat and set aside.
Lightly grease a 9×13-inch baking dish. Spread 1 cup of marinara sauce evenly on the bottom of the dish.
Place the browned chicken breasts in the baking dish on top of the sauce.
Spoon the remaining 1 cup of marinara sauce evenly over the chicken breasts.
Sprinkle shredded mozzarella cheese evenly over the sauced chicken breasts.
Cover the baking dish tightly with plastic wrap or aluminum foil. Refrigerate if making ahead, up to 24 hours.
When ready to bake, preheat the oven to 375°F (190°C). Remove the cover and bake uncovered for 25-30 minutes until the chicken is cooked through (internal temperature 165°F/74°C) and the cheese is melted and bubbly.
Remove from the oven and let rest for 5 minutes before serving.
Garnish with chopped fresh basil and serve hot.