Sweetbreads are the thymus (commonly mistaken as thyroid, even by professional chefs) or pancreas gland of a lamb, calf, or piglet. Their function in a live animal: helping with the immune system and digestion. Their function on a plate: deliciousness. Christophe Gerard, chef de cuisine of FARM at the Carneros Inn, blanches them in milk, then drains them and pan-fries them in butter. You don't need flour to get them nice and crisp.