Sweetbreads are expensive - roughly the price of trimmed fillet steak. That's one reason why they figure on haute cuisine menus. Although lightly flavoured, they are like luxurious edible sponges - great for absorbing and bringing together other tastes.
Escoffier, describing them as one of the finest delicacies, claimed: "They may be served for any meal, no matter how rich or sumptuous."
Since Escoffier's time, chefs have moved on in the way they handle sweetbreads. The classic technique was to soak, blanch and press them as a preliminary to braising, grilling, stewing or even roasting on a spit.
Martin Blunos of Lettonie, a two-Michelin-starred restaurant on the fringes of Bath, suggests that this fiddly basic preparation probably helped to disguise produce that lacked freshness.
"Sweetbreads are one of those raw materials like skate," says Blunos. "The moment they start to go off, the smell lets you know all about it." Suppliers tend to vacuum-pack them to extend a short shelf-life by a few days.
There are two pieces of sweetbread: the thymus and the pancreas. These glands are large only in young calves and will shrink as they grow towards maturity. In kitchen French, the thymus - the longer thinner strip - is known as the gorge or throat and the more chunky pancreas as the noix or cushion. This latter piece, weighing up to 300g, is the more desirable. When trimmed and served, it should deliver a couple of portions.
PREPARING THE SWEETBREAD CUSHION
Unpack the sweetbread and smell for freshness. It shouldn't have any unpleasant odour. Although the shape will vary from piece to piece, each noix will have a rounded side and a flatter surface.
To cut off the outer gristle, pull any loose pieces away from the sweetbreads and trim away, but don't throw them away because they will be used for the stock.
A transparent membrane covers the sweetbread and would make it shrink and toughen during cooking if it were left. It has to be removed in the way a chef skins a fish.
Loosen a piece of membrane on one side of the sweetbread with a sharp, thin-bladed knife. Keeping the blade almost flat on the work surface, pull the membrane against the knife edge so that it comes away. Turn over the sweetbread and repeat. Don't throw away the membrane.
If there are any traces of blood, they should be extracted carefully with the tip of a sharp knife.