Gelatin is a substance used for making, among other things, jellies, cold pies, confectioneries and capsules for medicine. It's also used in the preparation of beer and wine. It's extracted from the bones, cartilage, tendons and skins of animals, primarily cows but also pigs, by a process of boiling. Extracting gelatin from pig trotters is a lengthy process, but relatively straightforward.
Heat a large saucepan of water until it reaches a rolling boil. Add two pig trotters.
Boil the trotters for several hours at a high temperature until they partly or wholly disintegrate upon prodding.
Strain the contents of the saucepan and discard any bones or waste matter.
Leave the resulting liquid to stand overnight – don't put it in the fridge at this stage. By the next day, a layer of fat will have risen to the top. Skim this off with a ladle.
Pour the remaining liquid into jelly moulds, then place these in your fridge to set.