Preheat oven to 350°F (180°C) and line a loaf pan with parchment or foil.
Place ground chicken in a large bowl. Add onion, garlic, egg, ¼ cup parsley, ½ cup marinara, breadcrumbs, ⅓ cup Parmesan, Italian seasoning, salt, and pepper. Mix well with hands.
Transfer mixture to prepared pan and shape gently into a loaf.
Bake for 45 minutes.
Remove from oven, brush top with ¼ cup marinara, and sprinkle with mozzarella.
Return to oven and bake for another 15 minutes. Let cool for 10 minutes.
Meanwhile, melt butter in a skillet over medium heat. Add panko and garlic powder. Stir until golden, about 3–4 minutes. Let cool.
Stir in remaining 2 tablespoons Parmesan and 1 tablespoon parsley.
Top meatloaf with panko mixture. Serve with remaining marinara and fresh herbs.
