In a large mixing bowl, combine ground beef, grated Parmesan cheese, chopped parsley, egg, garlic powder, salt, black pepper, and breadcrumbs. Mix until just combined.
Form the mixture into 1 1/2-inch meatballs and place them on a baking sheet.
Bake the meatballs in a preheated 400°F oven for 20 minutes or until they are browned and cooked through.
In a baking dish, spread a thin layer of marinara sauce. Place the cooked meatballs on top of the sauce.
Spoon additional marinara sauce over each meatball, then sprinkle shredded mozzarella cheese on top.
Return the dish to the oven and bake for an additional 10 minutes, or until the cheese is melted and bubbly.