Place the gammon joint in a large pot and add the onions and pineapple juice. Bring to a boil over high heat.
2. Step
Once boiling, reduce the heat to medium, cover, and simmer for 70 minutes. (Gammon joints need to cook for 40 minutes per kilo (2 ¼ lbs),so if you are using a smaller or large gammon joint, adjust the cooking time accordingly.)
3. Step
Once cooked, carefully remove the gammon joint from the pan and place on a baking sheet to cool slightly.
4. Step
Preheat the oven to 375°F (190°C).
5. Step
Make the glaze: in a small pan over a medium heat, combine the Dijon mustard, pineapple juice, and maple syrup and bring to a boil. Cook for 10 minutes, or until slightly reduced and glossy.
6. Step
Carefully remove the skin from the gammon joint, using a small paring knife to help ease the fat away from the skin. Be sure to leave a small layer of fat on top of the gammon.
7. Step
Score the fat in a diamond pattern and push a clove into each cross section.
8. Step
Liberally brush the gammon joint with the glaze, making sure to reserve at least half of the glaze.
9. Step
Roast the gammon joint for 40 minutes, glazing again halfway through.
