Place the gammon joint into a large stock pot and add in the onions, celery, star anise, peppercorns, carrots and bay leaves.
Cover with water and cook for around two and a half to three hours (work on 20 minutes per 500g).
Once cooked, remove from the pan and set aside to cool until cool enough to handle.
Preheat the oven to 200oc.
Remove the skin but leave on the fat and score into diamond shapes.
Place a clove into each diamond until the whole fat is covered with cloves.
Mix the brown sugar, honey and mustard together in a bowl and brush all over the gammon.
Place in the oven for 25-30 minutes basting with the sauce every ten minutes.
Heat any remaining glaze in a pan and simmer until it becomes concentrated and thick and sticky.
Pour over the cooked gammon or serve on the side.