Place gammon ingredients, except for the water and fruit, in pot. Ensure gammon is submerged in liquid, topping up with water if needed. Bring to the boil. (Place a plate or something heavy on top to keep gammon submerged.)
Cover with a tight-fitting lid and boil for 35–40 minutes.
Remove from heat and wrap the entire pot in a blanket.
Leave overnight or for at least 12 hours to continue slow-cooking with residual heat.
Remove gammon from liquid, peel off skin and place on a roasting tray or in an oven dish.
Score gammon fat in a criss-cross pattern or to your liking, careful not to cut through the meat.
Preheat oven to 200°C.
To make glaze, combine all ingredients, except for the whisky, in a small pot. Simmer for 5–8 minutes to infuse and reduce slightly. Remove from heat and add whisky, if using.
Brush gammon liberally with about half the glaze.
Roast for 20–25 minutes, glazing every 5–10 minutes, or until fat is golden brown.
Rest for 10 minutes before slicing.
Serve sliced on a platter with pan juices and cherries or sliced stone fruit.