In a large bowl, combine the ground beef, breadcrumbs, Parmesan cheese, egg, garlic, Italian seasoning, salt, and pepper. Mix until well combined.
Take a small amount of the meat mixture and flatten it in your hand. Place a cube of mozzarella cheese in the center and wrap the meat around it, forming a ball. Repeat with the remaining meat and cheese.
Heat the olive oil in a large skillet over medium heat. Add the meatballs and cook until browned on all sides, about 5-7 minutes.
Pour the marinara sauce over the meatballs in the skillet. Cover and simmer for 15-20 minutes, or until the meatballs are cooked through and the cheese is melted.

Serve the meatballs hot, with your choice of sides.
Variations & Tips
For a lighter version, you can use ground turkey or chicken instead of beef. If you have picky eaters, consider using different cheeses like cheddar or gouda for a different flavor profile. You can also add finely chopped spinach or grated zucchini to the meat mixture for a hidden veggie boost. For a spicy kick, add a pinch of red pepper flakes to the meat mixture.