Prepare the Meatballs: In a bowl, mix ground turkey, spinach, garlic, breadcrumbs, egg, salt, pepper, Italian seasoning, and Parmesan.
Stuff with Mozzarella: Take a small amount of the mixture, flatten it, place a mozzarella cube in the center, and seal the meat around it to form a ball.
Cook the Meatballs: Heat olive oil in a pan over medium heat. Cook the meatballs until browned on all sides and fully cooked (about 8–10 minutes). Remove and set aside.
Make the Sauce: In the same pan, add olive oil and garlic. Sauté for a minute, then pour in marinara sauce and red pepper flakes. Simmer for 5 minutes.
Combine & Serve: Add the meatballs to the sauce and let them simmer for a couple more minutes. Serve with pasta, bread, or on their own!