Method
Soak the gammon according to the supplier's instructions. Then tear off two very large pieces of foil and arrange one lengthways and the other widthways over your largest roasting tin. Place the gammon in the centre and bring the widthways piece of foil up first and seal the two ends together by folding over to form a kind of pleat. This should be done loosely so there is room for air to circulate around the gammon. Now bring the lengthways pieces up at each end and tuck these all round to seal what is now a parcel.
Place the parcel (in the tin) in the oven and let it bake for 20 minutes per pound (450 g) – that is 4 hours for a 12 lb (5.4 kg) piece or 4 hours 40 minutes for a 14 lb (6.3 kg) piece. About 30 minutes before the end of the cooking time, remove the gammon and increase the heat to gas mark 7, 425ºF (220ºC). Open up the foil and transfer the gammon to a work surface (with help!). Now drain off all the juices (and reserve these in a bowl: the bacon fat will solidify and can be used for frying and the jelly for enriching lentil or pea soups).
Next peel off all the skin – make a couple of horizontal incisions and you should be able to peel it off in strips, using a cloth to protect your hands from the heat. Now score the fat with criss-cross cuts, making a diamond pattern. Stud a clove into the centre of each diamond shape, then smother the mustard all over, using a palette knife to spread it evenly. Finally sprinkle the sugar all over and press it in with your hands.
Return the gammon to the tin and bake for a further 30 minutes or until it is a glazed, golden mahogany colour.
If it's to be served hot, leave it to rest for about 45 minutes before carving. If cold, leave it to cool slowly overnight.
