Preheat oven to 375°F.

Heat olive oil in a medium-size skillet over medium-high heat. Once hot, add onions and sauté until softened and slightly browned, about 4-5 minutes. Add garlic and oregano, and continue to cook for 2-3 minutes or until fragrant. Season with salt and pepper, and remove from heat; reserve and cool.

In a large mixing bowl, combine ground chicken, eggs, breadcrumbs, milk, Parm, parsley, chili flakes, salt and pepper with your hands. Be careful not to overmix.

Place a piece of parchment paper on a large baking sheet. Place the chicken mixture on the baking sheet and form it into a long loaf shape. Spoon ½ cup of marinara sauce over the top of the meatloaf. Bake in the oven for 50-55 minutes, or until the internal temperature reaches 160°F.

Preheat your broiler. Top the meatloaf with remaining ½ cup marinara sauce and shredded mozzarella. Broil until bubbly and browned on top, about 1-2 minutes.

Garnish with basil leaves, slice and serve.