Preheat your oven to 400°F (200°C). Grease a cast iron skillet or an oven safe skillet.
In a large mixing bowl, combine the ground chicken, breadcrumbs, grated Parmesan, egg, minced garlic, dried oregano, dried basil, onion powder, salt, pepper, and chopped parsley (if using). Mix until well combined, but do not overmix.
Using your hands or a cookie scoop, form the mixture into meatballs about 1½ inches in diameter. Place the meatballs on the prepared cast iron skillet.
Transfer the skillet to the oven and bake the meatballs in the preheated oven for 15 minutes, or until they are cooked through and slightly browned.
Remove the meatballs from the oven. Spoon marinara sauce over each meatball, ensuring they are generously coated. Sprinkle shredded mozzarella and additional Parmesan cheese on top of the sauced meatballs.
Return the meatballs to the oven and bake for an additional 5-7 minutes, or until the cheese is melted and bubbly.
Remove the meatballs from the oven and garnish with fresh chopped basil or parsley. Serve hot with pasta, on a sub roll, or as an appetizer.