Preheat the oven to 400°F (200°C).
Place each chicken breast between two sheets of plastic wrap and gently pound with a meat mallet or rolling pin to an even thickness of about 1/2 inch.
In a shallow bowl, combine the whole wheat breadcrumbs, grated Parmesan cheese, garlic powder, dried Italian seasoning, salt, and black pepper.
In another shallow bowl, whisk together the eggs and water until well combined.
Dip each chicken breast first into the egg mixture, allowing excess to drip off, then coat thoroughly with the breadcrumb mixture, pressing gently to adhere.
Heat olive oil in a large oven-safe skillet over medium-high heat.
Add the breaded chicken breasts and cook for 3-4 minutes on each side until golden brown.
Remove the skillet from heat. Spoon marinara sauce evenly over each chicken breast.
Sprinkle shredded mozzarella cheese evenly on top of the sauce.
Transfer the skillet to the preheated oven and bake for 12-15 minutes, or until the chicken is cooked through (internal temperature reaches 165°F) and the cheese is melted and bubbly.
Remove from oven and let rest for 5 minutes.
Garnish with fresh basil leaves if desired and serve hot.