[Mollejas de Res (Spanish)]
These come in two varieties, "throat sweetbreads" (thymus) and "heart sweetbreads" (pancreas), sometimes called "stomach sweetbreads". The larger, oval shaped heart sweetbreads are preferred by fancy restaurants, so it is the elongated shaped throat sweetbreads we can buy in markets here in Southern California. The two can be cooked together if both are available, and they taste pretty much the same. The photo specimen, a thymus, was 8 inches long, 4 inches wide, 1-1/4 inches thick and weighed 0.9 pound.
Sweetbreads are a highly superior (not just in my opinion) substitute for beef brains in any recipe calling for those. Brains are mostly mushy cholesterol, and carry a minute risk of mad cow disease.
More on Beef Innards
Mild, tender sweetbreads in flavorful sauces were once popular all over North America and most of Europe, but today are served mostly to connoisseurs in fancy restaurants. They are still popular in Mediterranean and some other ethnic cuisines, and are well worth your attention
Buying: You won't find these in your average supermarket, but ethnic meat markets, particularly those serving Latin American or Near Eastern communities may have them. You will generally find only the thymus as the pancreas fetches a higher price in the fancy restaurant trade.
The photo specimen was bought from a large multi-ethnic market here in Los Angeles. It was packed in a plastic tub, but other markets may have them in sealed vacuum pack bags or on a shrink wrapped foam tray. In regions without ethnic markets you will have to order from a specialty meat market, probably at a higher price. Buy them well before the expiry date and cook them right after purchase as organ meats are quite perishable (and market expiry dates tend to be over-optimistic).
Some "gourmet" recipes call for "milk fed veal sweetbreads", but we don't have those around here. They're probably all sent to fancy restaurants in New York and San Francisco, where they can fetch an outrageous price. Here in Los Angeles, world center for ethnic cuisines, we're fine with more robust flavors.
Yield: After soaking, par boiling and pressing as shown below, you will have about 46% of the weight as bought. Recipes almost always give the weight "as purchased" and expect the weight loss. Yield may be a little higher if all these steps are not followed.
Prep: The way they're sold around here, sweetbreads are pretty much ready to go, so step 1 may not be needed.