Meatball Mix: – 1/2 cup finely grated Pecorino Romano – 1/2 cup panko breadcrumbs – 2 eggs, beaten – 1 small yellow onion, shredded – 4 garlic cloves, finely grated – 1/4 cup finely chopped fresh parsley – 1 1/2 teaspoons kosher salt – 1/2 teaspoon freshly cracked black pepper – 8 ounces ground beef (80/20) – 8 ounces ground pork – Olive oil (for greasing hands and searing)
Sauce: – 1 (24-ounce) jar passata – 1/2 cup water – 2 tablespoons granulated sugar – 2 Parmesan rinds (optional) – 1 dried bay leaf – Kosher salt and freshly cracked black pepper, to taste
Make the Meatball Mix: Combine cheese, breadcrumbs, eggs, onion, garlic, parsley, salt, and pepper in a large bowl. Add ground beef and pork, and gently mix with hands until just combined.
Shape the Meatballs: With oiled hands, roll the mixture into 1½-inch balls (you should get 16–18 meatballs) and place them on a tray or plate.
Sear the Meatballs: Heat olive oil in a large pot over medium-high. Sear meatballs in batches until golden brown on both sides. Transfer to a plate.
Make the Sauce: Lower the heat and add the passata, water, sugar, Parmesan rinds (if using), and bay leaf. Stir to mix and loosen browned bits.
Simmer the Meatballs: Return the meatballs and their juices to the pot. Simmer, covered, for 25 minutes. Then uncover and cook for 10 more minutes. Season to taste and serve.