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.
02 - Form the mixture into 16-18 golf ball-sized meatballs, rolling gently between your palms to maintain a tender texture.
03 - Heat 2 tbsp olive oil in a large skillet over medium heat. Add meatballs in batches and brown on all sides for 5-6 minutes total. Transfer browned meatballs to a plate.
04 - Heat 2 tbsp olive oil in the same skillet. Add onion and cook for 3-4 minutes until softened. Add garlic and sauté for 1 minute until fragrant.
05 - Stir in crushed tomatoes, tomato paste, basil, oregano, sugar, salt, pepper, and red pepper flakes (if using). Bring to a gentle simmer.
06 - Return browned meatballs to the sauce. Cover and simmer on low heat for 20-25 minutes, turning meatballs occasionally, until cooked through and sauce thickens.
07 - Taste and adjust seasoning as needed. Garnish with fresh basil or parsley before serving over pasta, polenta, or with crusty bread.