Caul is the lacy lining of a pig’s stomach. It is quite difficult to get hold of but you should be able to order it through your butcher. It must be soaked in cold water for 24 hours first, which makes it easier to use, then drained. It’s used almost like cling film, rolled around meat or a meaty mixture, to which it will cling. If caul is unavailable, cook without a covering or use buttered foil.
Sausage skins are the intestines of the pig, and must be ordered from your butcher as well. They, too, need to be soaked for several hours and rinsed before use.