Traditional American baking is often based on lard or solid vegetable shortening, but in England, the favored fat for pies, pastries, and those famous steamed puddings like Apple Hat and Sussex Pond Pudding is suet—which, properly speaking, is the pure white fat encasing beef kidneys. Suet’s great value is that it melts as the dough cooks, not only enriching the finished product but leaving little spaces in it for a loose, soft finished product. Good suet, which should be odorless, dry to the touch, firm, and well cleaned, imparts no beefy flavor. Buy fresh suet directly from a butcher, if possible; that sold in supermarkets is often intended as bird food and may be of inferior quality. For best results, chill suet before grating it.
The Skinny On Suet