In a large bowl, combine all of the meatball ingredients (ground chicken, onion, garlic, breadcrumbs, ½ cup parmesan, egg, chopped parsley, italian seasoning, salt and pepper). To mix everything, best to use your hands but you can also use a spatula if you like, and mix everything together until just combined. Do not over mix.
Add marinara to a pan (that has a lid), and heat it over gentle heat as you portion out the meatballs.
Use a 3 tablespoon cookie scoop to portion out meatballs, to make them round you can roll them between your hands (wet your hands as needed with a little bit of water so the meatball mixture does not stick to your hands).
And immediately drop the meatballs into the simmering marinara sauce.
Cover with a lid, and simmer over low heat for 15 minutes flipping the meatballs halfway through. The internal temp of the meatballs must reach 165°F/74°C.
Preheat the broiler, then sprinkle the remaining parmesan all over the meatballs followed by all the mozzarella. Place under the broiler for 3-5 minutes or until the top is bubbling and browned. Garnish with fresh basil and serve over pasta, rice, or garlic bread.