Start by setting your oven to 400°F (200°C). Line a baking sheet with foil and lightly spray it with nonstick cooking spray. This ensures the meatballs don’t stick and cleanup is easy.

Grab a large bowl and mix together the ground beef, egg, breadcrumbs, Parmesan cheese, minced garlic, onion, parsley, salt, and pepper. Be gentle when mixing to avoid overworking the meat, which can lead to tough meatballs. If the mixture feels a little dry, add a spoonful of water.

Cut the mozzarella into small cubes. Take a scoop of the meat mixture and flatten it into a small patty. Place a mozzarella cube in the center and carefully wrap the meat around it, sealing all edges tightly. Repeat until all the meatballs are made.

Arrange the prepared meatballs on your baking sheet and pop them into the preheated oven. Bake for about 17–20 minutes, flipping them halfway through for even cooking. When done, they should be golden brown with a gooey cheese center.

Serve the warm meatballs with your favorite marinara sauce. Sprinkle fresh parsley and extra Parmesan on top for a finishing touch that adds both flavor and color.