Peel and cut 1 onion in half. To a large pot or Dutch oven, place ham, the onion and pour over top, the 2 liter bottle of coca-cola. On a medium-high heat, allow to cola to come to a boil. Reduce heat to medium-low and cover, not tightly with lid, and allow to cook for 2 1/2 hours. It is 1 hour for every 2 pounds.
Preheat oven to 500 degrees F.
Pull the ham from the pot, and allow to rest on a cutting board reserving the cooking liquid. Using a sharp knife, trim the skin, leaving a thin layer of fat on the ham. Using the knife, score the fat diagonally into large diamond cut.. In each diamond pierce the fat with 1 clove. Spread the molasses over the meat. Gently pat the powdered mustard and sugar around the meat, so it sticks to the molasses. Line a roasting pan with aluminum foil. Gently place the ham in the roasting pan. Cook the ham for about 10 minutes or until glaze is burnished and bubbly.
For braising the ham in advance and then letting the ham cool, take ham from the refrigerator, glaze it according to the recipe, and give it 30 to 40 minutes to sit at room temperature. Place in a 350 degree F oven for 30 to 40 minutes, then turning up the heat if you think it needs a more crispy exterior.