What caul fat means
Caul fat is a thin, delicate membrane of fat that surrounds the internal organs of animals, mainly pigs but also sheep and cows. It looks like a sheet of fine, lacy netting, with a web of fatty veins running through a thin, almost transparent layer. It is also called caul, lace fat or, in French, crépine. In cooking, caul fat is used as a natural wrapping for meat.
Pieces are wrapped around food before it is cooked, and as it heats, the fat slowly melts and bastes the meat, keeping it moist and adding flavour, while the membrane holds the shape together. By the end of cooking, the caul has mostly melted away, leaving only a thin, crisp lacy pattern. It is traditionally used in British faggots, which are balls of pork offal, onions and breadcrumbs, and in French crépinettes, which are flat sausages wrapped in caul instead of a casing. It is also used to wrap terrines, pâtés, burgers, meatballs, stuffed joints of lamb or pork, game, lean cuts of venison and liver, and some fish.
Caul fat is sold by butchers, fresh, frozen or salted, and often needs ordering in advance. Before use, it is soaked in cold water, sometimes with a little vinegar, to soften it, then gently unfolded, cut into pieces and wrapped around the food. You will see caul fat in traditional British and French recipes.