Preheat your oven to 200°C (400°F) and line a baking sheet with foil.

In a skillet heated to medium, add olive oil, diced onion, and minced garlic. Sauté for about 3-5 minutes until fragrant.

In a large mixing bowl, combine ground chicken, cooled sautéed onion and garlic, breadcrumbs, milk, Parmesan cheese, egg, parsley, Italian seasoning, and salt. Mix gently.

Shape about two-thirds of the mixture into a loaf on the prepared baking sheet. Create a well in the center and fill it with mozzarella cheese, then cover with the remaining mixture.

Spread marinara sauce over the top of the meatloaf.

Bake for approximately 45 minutes until firm and cooked through.

Mix panko breadcrumbs, melted butter, and Parmesan cheese in a bowl for topping. Set aside.

Remove meatloaf from the oven, sprinkle shredded mozzarella and the panko mixture on top, and return to the oven for an additional 15-20 minutes.

Let the meatloaf rest for about 10 minutes before slicing.