Sweetbreads on mushroom (morel) risotto. Sweetbreads or ris are culinary names for the thymus (also called throat, gullet, or neck sweetbread) or the pancreas (also called heart, stomach, or belly sweetbread), especially of calf (ris de veau) and lamb (ris d'agneau), and, less commonly, of beef and pork.ocky Mountain oyster, prairie oyster, or lamb fries). The heart sweetbreads are more spherical in shape, and surrounded symmetrically by the throat sweetbreads, which are more cylindrical in shape.