In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the finely diced onion and sauté for about 3-4 minutes until translucent. Stir in the minced garlic and cook for an additional minute until fragrant. Remove from heat and let cool slightly.
In a large mixing bowl, combine the ground chicken, sautéed onion and garlic, beaten egg, milk, bread crumbs, freshly grated parmesan cheese, chopped parsley, Italian seasoning, salt, black pepper, and crushed red pepper flakes. Mix everything together until just combined.
Using your hands, divide the chicken mixture into equal portions and shape them into patties, about 3-4 inches in diameter.
In the same skillet, heat the remaining tablespoon of olive oil over medium-high heat. Once hot, add the chicken patties to the skillet. Cook for about 5-6 minutes on each side, or until they are golden brown and cooked through.
Preheat your oven to 375°F (190°C). In a baking dish, pour a layer of marinara sauce on the bottom. Place the cooked chicken patties on top of the sauce. In a small bowl, mix together the remaining marinara sauce and tomato paste, then pour this mixture over the patties. Top with shredded mozzarella cheese and sprinkle with additional grated parmesan.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. After 20 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Once baked, remove from the oven and let it cool for a few minutes before serving. Garnish with additional chopped parsley for a fresh touch.
