Beef and Mortadella Meatballs in Tomato Sauce

• ¼ cup olive oil
• 1 medium onion, finely chopped
• 1 medium carrot, finely chopped
• 1 celery stalk, finely chopped
• ½ cup tomato paste
• 1 28-oz. can crushed tomatoes
• 1 cup heavy cream
• 1 teaspoon kosher salt, plus more

Freshly ground black pepper

• 1 pound ground beef, preferably chuck
• ½ pound mortadella, cut into ¼" pieces
• 2 large eggs
• ⅓ cup fine fresh breadcrumbs
• ¼ cup chopped fresh parsley
• 2 tablespoons chopped fresh oregano

Grated Grana Padano cheese (for serving)

1. Heat oil in a large heavy pot over medium-high. Add onion, carrot, and celery; season with salt and pepper. Cook, stirring often, until vegetables are soft and translucent, 10–15 minutes. Add tomato paste and cook, stirring, until darkened, about 4 minutes. Stir in tomatoes and cream and bring to a boil. Reduce heat; season with salt and pepper. Simmer while you form the meatballs.
2. Using a fork or your hands, mix beef, mortadella, eggs, breadcrumbs, parsley, oregano, and 1 tsp. salt in a large bowl until evenly combined. Form mixture into 1½”- diameter balls, packing fairly firmly (you should have about 26) .
3. Add meatballs to sauce, cover pot, and simmer until meatballs are cooked through and very tender, 40–45 minutes.
4. Serve topped with a generous amount of Grana Padano.
5. Do Ahead: Meatballs (without cheese) can be made 2 days ahead. Let cool; cover and chill. Reheat gently in sauce before serving.