Haslet is a very dark-coloured British sausage made from pig's pluck (heart, liver and lungs.)
It can be made as a sausage or a meatloaf.
The meat is finely minced to make a forcemeat, which is then flavoured with herbs such as sage. The meat is then bound together with wheat flour or breadcrumbs, and then wrapped in caul fat.
In Wales, the mixture is more likely to be just pig's liver, along with onion and potato.
Some butchers make special versions without wheat flour for coeliacs.
In place of caul fat, you may poke in small pieces of lard here and there. Some people then wrap it in foil.
Particularly traditional in Lincolnshire, England.
You cook it by baking. Serve cold in slices.
"... and so home to dinner with my wife to a good hog's harslet, a peice of meat I love but have not eat of I think this seven year."
Literature & Lore
-- Samuel Pepys, 10th March, 1664.
The world "Haslet" comes from an old French word for "entrails."