Osso buco is a cut of meat from the shank of cattle. It's a cross-cut section of the leg, including both meat and a bone with marrow. The marrow adds a rich, buttery flavor when slow-cooked, a hallmark of the dish.
The word Osso Bucco actually means "bone with a hole" in Italian. This cut is wrapped around a bone full of marrow so it best cooked low and slow for quite some time to savor the amazing mouth watering flavor and to get your meat to fall right off the bone.