Wash the ham hock and place in a large saucepan and add the Guinness, carrots, apple, parsley, onion and peppercorns. Add enough cold water to cover.
Bring to the boil, turn down the heat and simmer with the lid partly on for about 2½ hours until the meat is starting to come off the bone.
Leave to cool in the liquid. Drain and keep all the juices. (see tip below)
Pat the ham hock dry with kitchen paper. Using a knife carve away the skin leaving some of the fat.
Mix together the mustard, molasses and honey and spoon all over the ham.
Pre-heat the oven to 180C/gas Mark 4 and bake for about 40 minutes until starting to brown, taking care not to burn, basting halfway through.
Shred the ham into pieces or simply serve in slices with its juices from the pan.
The cooking liquid can be blended until smooth and used as a stock. It can be a base for a soup, a sauce or simply use as a gravy to go with the ham.