Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large bowl, combine the ground beef, breadcrumbs, Parmesan cheese, parsley, egg, garlic, onion powder, Italian seasoning, salt, and black pepper. Mix until well combined.
Take a small amount of the meat mixture (about 2 tablespoons) and flatten it in your hand. Place a cube of mozzarella cheese in the center and fold the meat around the cheese to form a ball. Repeat with the remaining mixture.
Place the meatballs on the prepared baking sheet. Drizzle with olive oil.
Bake in the preheated oven for 20-25 minutes, or until the meatballs are cooked through and browned.
While the meatballs are baking, heat the marinara sauce in a saucepan over medium heat.
Once the meatballs are done, remove them from the oven and transfer them to the saucepan with the marinara sauce. Simmer for 5 minutes to allow the flavors to meld.
Serve the meatballs hot, garnished with fresh basil if desired.