Place into a large pot, and fill with enough water to cover. Bring to a boil and cook for 1 hour, replenishing water as needed.
Drain.
Meanwhile, stir together the brown sugar, soy sauce and mustard in a small bowl. Set aside until the ham is done.
Place the ham halves into a glass or ceramic baking dish with the cut sides facing up. Cover the ham with the brown sugar mixture. Cook in the microwave for 15 minutes. Slice and serve.
