Put the gammon in a pan, skin side down if it fits like, add the onion then pour over the cola.
Bring to the boil, reduce to a good simmer, put the lid on, though not tightly, and cook for 1 hour a kilo. If gammon is straight from fridge add 15mins to cooking time.
Preheat oven to 240°C/gas 9
Take the ham out of the pan and let the ham cool a little for ease of handling. (You can let it cool completely then finish off the cooking at some later stage if you want).
Remove skin, leaving a thin layer of fat. Score the fat with a sharp knife to make fairly large diamond shapes, and stud each diamond with a clove. Then carefully spread the golden syrup over the fat. Then gently pat the mustard and sugar onto the sticky fat.
Cook for approximately 10 minutes or till the glaze is dark and bubbly. If you left the ham after the simmering, cook for 30-40 minutes at 180°C instead
