Heat olive oil in a sauté pan over medium heat. Add diced onion and minced garlic, cooking until softened, about 5-7 minutes.

In a mixing bowl, combine ground chicken, cooled onion and garlic, breadcrumbs, Parmesan cheese, Italian seasoning, parsley, milk, egg, and a pinch of salt.

On a baking sheet lined with parchment paper, form two-thirds of the meat mixture into a rectangular shape, making a well in the center for mozzarella.

Preheat oven to 200°C (400°F). Spoon marinara sauce over the meatloaf and bake for 45 minutes.

Mix panko breadcrumbs, additional Parmesan cheese, melted butter, and parsley. After the initial baking, remove and sprinkle mozzarella and breadcrumb mixture.

Return meatloaf to the oven and bake for an additional 15-20 minutes until golden brown.

Remove from oven and let rest for 10 minutes before slicing.