In a large mixing bowl, combine ground beef, egg, finely diced onion, minced garlic, chopped parsley, Panko breadcrumbs, parmesan cheese, dried basil, dried oregano, salt, and pepper. Mix thoroughly until all ingredients are evenly distributed.

Cut the fresh mozzarella into approximately 1/2 inch cubes. Set aside.

Using about 2 tablespoons of the meat mixture per meatball, flatten the meat in your hand, place a mozzarella cube in the center, then cover the cheese completely with meat and roll into a ball. Repeat this process to make about 12 meatballs.

Heat olive oil in a large nonstick pan over medium to high heat.

Add the meatballs and cook, browning one side, then carefully flip to brown the other side, ensuring a nice crust forms on all sides.

Once browned, pour marinara sauce over the meatballs in the pan. Reduce heat to medium-low, cover the pan, and let the meatballs simmer for about 10 minutes.

Flip the meatballs halfway through cooking to ensure even heat distribution and that the cheese inside melts properly.

Serve the mozzarella stuffed meatballs hot, spooned with extra marinara sauce over your favorite pasta.

Garnish with fresh parsley and additional parmesan cheese if desired.