01 - Combine ground beef, breadcrumbs, Parmesan, egg, milk, garlic, parsley, oregano, salt, and pepper in a large bowl. Mix gently until just combined. Avoid overworking the meat to maintain tenderness.
02 - Form the mixture into 16 to 18 golf ball-sized meatballs, ensuring uniform size for even cooking.
03 - Heat 2 tablespoons olive oil in a large skillet over medium heat. Add meatballs in batches, browning on all sides for 5 to 6 minutes total. Transfer browned meatballs to a plate and set aside.
04 - In the same skillet, heat 2 tablespoons olive oil. Add chopped onion and cook for 3 to 4 minutes until softened. Add minced garlic and sauté for 1 minute until fragrant.
05 - Stir in crushed tomatoes, tomato paste, dried basil, dried oregano, sugar, salt, pepper, and red pepper flakes if using. Bring mixture to a gentle simmer.
06 - Return browned meatballs to the sauce. Cover and simmer on low heat for 20 to 25 minutes, turning meatballs occasionally, until cooked through and sauce has thickened.
07 - Taste and adjust seasoning as needed. Garnish with fresh basil or parsley before serving over spaghetti, polenta, or with crusty bread.