- Preheat oven to 325 degrees. Place ham in roasting pan, cut side down, fat side up. Score ham in a cross-hatch pattern 1-inch wide, about ½-inch deep.
- Pour cider, brandy, and water over ham. Cover with foil tent, making sure foil does not touch ham. Cook until internal temperature reaches 135 degrees, about 3 to 4 hours, basting every 30 minutes. Remove from oven and remove foil.
- Raise oven temperature to 375 degrees. Combine brown sugar and mustard; slather on ham and return to oven uncovered. Cook until golden, about 30 minutes. Remove from oven and let rest for 20 minutes before serving.