Preheat oven to 425°F. Line a baking sheet with parchment paper and spray lightly with cooking spray.
In a shallow bowl, combine panko breadcrumbs, Parmesan cheese, Italian seasoning, garlic powder, salt, and pepper. Place beaten egg whites in another shallow bowl.
Pat chicken breasts dry with paper towels. Dip each chicken breast in egg whites, letting excess drip off, then coat thoroughly in breadcrumb mixture, pressing gently to adhere.
Place breaded chicken on prepared baking sheet. Spray tops lightly with cooking spray. Bake for 15 minutes.
Remove from oven and spoon 2 tablespoons of marinara sauce over each chicken breast. Top each with 2 tablespoons of mozzarella cheese.
Return to oven and bake for an additional 8-10 minutes, until chicken reaches an internal temperature of 165°F and cheese is melted and bubbly.
Let rest for 3 minutes. Garnish with fresh basil and serve with remaining marinara sauce on the side. Pair with zucchini noodles or a side salad for a complete meal!