Step 1: In a large bowl, combine ground beef, ground pork, breadcrumbs, Parmesan, parsley, eggs, garlic, oregano, salt, and pepper. Mix gently until just combined.
Step 2: Form the mixture into 1.5-inch meatballs (about 20 meatballs).
Step 3: Heat olive oil in a large skillet over medium heat. Brown meatballs on all sides, about 5-7 minutes total. Remove and set aside.
Step 4: In the same skillet, add onion and cook until softened, about 3 minutes. Stir in tomato paste and cook for 1 minute.
Step 5: Add crushed tomatoes, sugar, and water. Bring to a simmer.
Step 6: Return meatballs to the skillet, cover, and simmer for 20 minutes, until meatballs are cooked through and sauce has thickened.
Step 7: Serve hot over pasta or with crusty bread, garnished with extra Parmesan if desired.