1. Preheat oven to 350 degrees. Place ham on a roasting rack in a large roasting pan. Cover tightly with foil. Bake, rotating pan halfway through, 4 hours.

2. Meanwhile, make glaze: In a small saucepan, heat jam until liquefied. Strain through a fine sieve into a small bowl; discard solids. Stir in mustard, maple syrup, rum, and garlic.

3. After 4 hours, remove ham from the oven, and brush with glaze. Continue baking the ham, glazing every 15 minutes, until an instant-read thermometer inserted into thickest part of the ham (avoiding bone) registers 140 degrees, about 1 hour more. Remove from oven, and transfer to a carving board or platter. Garnish ham with bay leaves and kumquats, if desired. Slice thinly around the bone, and serve hot or at room temperature.