In a large bowl, combine the ground beef, breadcrumbs, grated Parmesan cheese, milk, egg, minced garlic, chopped parsley, salt, and black pepper. Mix until well combined.
Shape the mixture into meatballs, about the size of a golf ball.
Heat the olive oil in a large skillet over medium heat. Add the meatballs and cook until browned on all sides, about 8-10 minutes.
Add the marinara sauce to the skillet with the meatballs. Reduce the heat to low and simmer for 20-25 minutes, until the meatballs are cooked through.
Garnish with fresh basil leaves and serve hot. Enjoy!