Preheat your oven to 200°C (400°F) and prepare a baking sheet with aluminum foil and cooking spray.

Heat olive oil in a medium skillet and sauté diced onion and minced garlic until fragrant, about 5 minutes.

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

Shape two-thirds of the meat mixture into a loaf on the baking sheet and create a trench for the mozzarella.

Encapsulate the mozzarella with the remaining meat mixture to form a traditional meatloaf shape.

Spread marinara sauce evenly on top of the meatloaf and bake for 45 minutes until it reaches an internal temperature of 74°C (165°F).

After 45 minutes, sprinkle mozzarella, panko, Parmesan, melted butter, and parsley on top, then return it to the oven for 15-20 minutes.

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