In a large bowl, combine ground beef, breadcrumbs, grated Parmesan cheese, chopped parsley, egg, minced garlic, salt, black pepper, and Italian seasoning. Mix until well combined.

Shape the mixture into meatballs, about 1 inch in diameter.

Heat a large skillet over medium heat and add a drizzle of olive oil. Once hot, add the meatballs in batches, cooking until browned on all sides, about 5-7 minutes. Remove the meatballs from the skillet and set aside.

In the same skillet, pour in the marinara sauce and bring it to a simmer.

Return the meatballs to the skillet, nestling them into the sauce. Cover and cook for an additional 10 minutes, allowing the meatballs to cook through.

Preheat your oven's broiler.

Once the meatballs are cooked, sprinkle the shredded mozzarella cheese over the top. Transfer the skillet to the oven and broil for 2-3 minutes, or until the cheese is bubbly and golden brown.

Remove from the oven and let cool slightly before serving.

Garnish with additional parsley if desired and serve warm.