Preheat your oven to 200°C (400°F) and prepare a baking sheet by lining it with foil and lightly spraying with cooking spray.

In a medium skillet, heat 1 tablespoon of olive oil over medium heat. Once hot, add the finely diced onion and minced garlic, sauté for about 5 minutes until softened.

Transfer the mixture to a bowl to cool completely before adding it to the meatloaf.

In a large mixing bowl, combine the cooled onion and garlic mixture with ground chicken, seasoned breadcrumbs, and milk. Add grated Parmesan cheese, beaten egg, chopped parsley, Italian seasoning, and salt. Mix gently.

On the prepared baking sheet, spread two-thirds of the meat mixture into a rectangle about one inch thick, and add sliced mozzarella cheese in the center before topping with the remaining meat mixture.

Spread marinara sauce over the top of the formed meatloaf. Place the baking sheet in the preheated oven and bake for about 45 minutes.

Prepare the crunchy topping by mixing together panko breadcrumbs, grated Parmesan cheese, melted butter, and remaining parsley.

After 45 minutes, remove the meatloaf from the oven, sprinkle shredded mozzarella cheese over the top, and return to the oven for an additional 15 to 20 minutes.

Allow the meatloaf to rest for 10 minutes before slicing.