Sweetbreads are the thymus glands that come from veal, young beef, lamb and pork. There are two kinds of glands, and elongated lobe it the throat, and a large one near the heart. The two of them are connected by one tube that is removed before they go to the market. The heart sweetbread is the most expensive and the most delectable. It has a firm, creamy texture. Sweetbreads from veal are tender, ones from beef are tougher, and the ones from pork have a strong flavor. Availability; young calf and beef are available year round in specialty markets. Lamb and pork may have to be special ordered.
Buy sweetbreads that are white, plump and firm. They need to be prepared within 24 hours of buying. Before cooking they must be soaked in several batches of acidulated water, and have their membranes removed.