Heat oven to 375°F. In a large bowl, mix the ground beef, breadcrumbs, Parmesan, egg, garlic, Italian seasoning, salt, and pepper until just combined. Roll into 12 meatballs.
Heat an oven-safe skillet over medium-high heat. Brown the meatballs 2 minutes per side, then pour in the marinara sauce.
Transfer the skillet to the oven and bake 12–15 minutes, until the meatballs reach 160°F inside.
Nestle a mozzarella ball on top of each meatball, then press a black olive slice into each as the pupil. Return to the oven 3 minutes to melt.
Sprinkle with fresh basil and serve straight from the skillet!