Soak a 5 kg gammon in cold water for 12 hours.
Pour off the water and wash the gammon in fresh cold water.
Place in a deep pan, cover with cold water, bring to the boil and skim, then simmer gently for 4 hours.
When cooked, remove the skin, trim off some of the fat and carve into thin slices.
Serve moistened with a little of the cooking liquor and, by tradition, accompanied with pease pudding.
To test if the gammon is cooked the small mustard bone can be pulled out of the knuckle end and the meat can be easily pierced with a needle at its thickest point.