Preheat your oven to 200°C (400°F) and line a baking sheet with foil, lightly spraying it with cooking oil.

Sauté onion and garlic in olive oil over medium heat for about 5 minutes until softened. Let cool.

In a bowl, combine ground chicken, cooled onion & garlic, breadcrumbs, milk, Parmesan cheese, egg, parsley, Italian seasoning, and salt. Mix until combined without overmixing.

Shape two-thirds of the mixture onto the baking sheet, flattening it to about 1 inch thick, then add mozzarella slices in the center and cover with the remaining mixture.

Spread marinara sauce over the meatloaf and bake for 45 minutes or until the internal temperature reaches 74°C (165°F).

Mix panko breadcrumbs, extra Parmesan, melted butter, and parsley for topping. After 45 minutes, sprinkle this mixture and shredded mozzarella over the meatloaf.

Return to oven and bake for another 15-20 minutes, until the topping is golden brown and crispy.

Let the meatloaf rest for about 10 minutes before slicing and serving.