Suet is the hard, crumbly white fat that encases the kidneys and loins of cattle (and sheep) — used raw and unrendered, grated or shredded, rather than melted first. Higher-melting and drier than any other cooking fat, it is the defining ingredient of British steamed and boiled puddings, dumplings, mincemeat and traditional pastry, where it stays solid until the batter is hot enough to set and then melts out to leave a light, open, spongy crumb.