01 - Preheat oven to 375°F. Line a loaf pan with parchment paper or lightly grease it.
02 - In a large mixing bowl, combine ground chicken, Parmesan, mozzarella, onion, garlic, parsley, breadcrumbs, egg, milk, marinara sauce, Italian seasoning, salt, and pepper. Mix until just combined — avoid overmixing to keep the loaf tender.
03 - Transfer the mixture to the prepared loaf pan and gently press it in to form an even loaf.
04 - Spread an additional few tablespoons of marinara sauce over the top for extra flavor and moisture.
05 - Bake for 45–50 minutes, or until the meatloaf is golden, set, and the internal temperature reaches 165°F.
06 - Let rest for 10 minutes before slicing. Serve with additional marinara sauce if desired.