In a large mixing bowl, combine the ground chicken, freshly grated Parmesan cheese, gluten-free breadcrumbs, minced garlic, and grated onion. Add in the Italian seasoning and the egg to bind the mixture. Use your hands to mix everything together until well-incorporated, but be careful not to overmix.

Take a handful of the meat mixture and flatten it in your palm. Place a small cube of mozzarella cheese in the center, then fold the mixture over to seal the cheese inside. Roll it gently into a ball shape, ensuring no cheese is visible.

In a large skillet, heat a couple of tablespoons of olive oil over medium heat until it shimmers. Carefully add the formed meatballs, ensuring they are spaced out. Cook for about 5-7 minutes, turning occasionally, until they are golden brown on all sides.

Once the meatballs are browned, pour in your favorite marinara sauce or crushed tomatoes into the skillet. Stir gently to coat the meatballs and bring the mixture to a simmer. Cover the skillet and let them simmer on low for 15-20 minutes.

After simmering, carefully transfer the Chicken Parmesan Meatballs with Mozzarella to a serving dish. Garnish with freshly chopped basil or parsley and enjoy!