To give these meatballs a flavor boost and make them extra tender, chef Ludo Lefebvre adds finely chopped fat back and prosciutto to the meat mixture.
In a medium saucepan, heat the olive oil until shimmering. Add the garlic and cook over moderate heat, stirring, until fragrant, about 2 minutes. Add the tomatoes, crushed red pepper, oregano, sugar, and salt. Simmer over low heat, stirring occasionally, until the sauce is slightly thickened, about 1 hour. Stir in basil and remove from the heat.
In a large bowl, combine the veal, pork, beef, fat back, prosciutto, bread, fennel seeds, crushed red pepper, oregano, parsley, and salt; mix well. In a small bowl, beat the eggs with the ricotta, parmesan, and milk. Add the wet ingredients to the meat mixture; mix well. Form the mixture into 12 to 14 meatballs (about ¼ cup each).
In a large, deep skillet or braising pan, heat the grapeseed oil until shimmering. Add the meatballs and cook over moderate heat, turning, until browned all over, about 10 minutes. Add the sauce to the meatballs. Cover and braise in the oven until the meatballs are very tender and the sauce is reduced, about 2 hours. Serve in bowls, passing more parmesan at the table.