01 - In a large bowl, gently mix ground beef, breadcrumbs, Parmesan, milk, egg, garlic, onion, parsley, oregano, salt, and pepper until just combined, avoiding overmixing.
02 - Form the mixture into 16 to 18 meatballs, approximately 1.5 inches in diameter each.
03 - Heat 2 tablespoons olive oil in a large skillet over medium heat. Brown the meatballs in batches, turning to sear all sides evenly, about 5 to 7 minutes total. Transfer to a plate.
04 - In a large saucepan, warm 2 tablespoons olive oil over medium heat. Sauté chopped onion until translucent, approximately 3 to 4 minutes. Add garlic and cook for an additional 30 seconds until aromatic.
05 - Incorporate crushed tomatoes, dried basil, oregano, red pepper flakes if using, sugar, salt, and pepper. Bring the sauce to a gentle simmer.
06 - Return the browned meatballs to the saucepan. Cover and simmer gently for 20 to 25 minutes, stirring occasionally and turning the meatballs to ensure even cooking and thickening of the sauce.
07 - Taste and adjust seasoning as needed. Garnish with freshly chopped basil or parsley and serve hot over pasta or with crusty bread.