Step 1: In a large bowl, gently combine the ground beef, ground pork, fresh breadcrumbs, grated Pecorino Romano cheese, chopped fresh parsley, minced garlic, milk, lightly beaten eggs, salt, black pepper, and optional red pepper flakes. Use your hands to mix until just combined, being careful not to overmix, which can make the meatballs tough.
Step 2: Lightly wet your hands and roll the mixture into approximately 24 meatballs, each about 1.5 to 2 inches in diameter. Place them on a baking sheet.
Step 3: Heat 2 tablespoons of olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Working in batches, brown the meatballs on all sides until golden brown, about 2-3 minutes per side. They don’t need to be cooked through, just browned. Remove the browned meatballs and set aside.
Step 4: In the same pot, add a little more olive oil if needed. Sauté the finely diced onion over medium heat until softened and translucent, about 5-7 minutes.
Step 5: Pour in the crushed tomatoes and tomato sauce. Add the bay leaf and a pinch of sugar if your tomatoes are acidic. Bring the sauce to a gentle simmer, scraping up any browned bits from the bottom of the pot.
Step 6: Carefully return the browned meatballs to the simmering sauce. Ensure they are mostly submerged. Reduce the heat to low, cover the pot, and let the meatballs simmer for at least 1 hour and 45 minutes, or up to 3 hours, stirring occasionally. The longer they simmer, the more tender and flavorful they become.
Step 7: Once the meatballs are tender and the sauce has thickened, remove the bay leaf. Taste and adjust seasoning if necessary. Serve hot with your favorite pasta, polenta, or in a submarine sandwich. Garnish with fresh parsley or basil.