Place the gammon in a saucepan and add the onion and pineapple juice. Bring to a boil, then simmer over low heat for about an hour (40 minutes/kilo).
Once cooked, carefully remove the gammon to a plate. Keep a cup of the cooking jus.
Meanwhile make the glaze: combine the mustard, pineapple juice and honey in a small pan and bring to the boil over a medium heat. Cook for about 10 minutes, until it reduces to a glossy syrup. Set aside.
Preheat the oven to 180°C.
Remove the skin from the gammon joint, using a sharp knife.
Pour the cooking jus you set aside into a baking dish. Place the gammon onto a rack and brush it generously with the glaze, then stick the pineapple wedges to the skin with the cloves. Brush again with the glaze. Carefully place the rack with the gammon in the tray and bake for about 30 minutes in the middle of the oven, basting the meat with the remaining glaze a couple of times.
Serve warm or let it cool before carving.