This Easter favorite uses a fully cooked cured ham, which only needs to be warmed through.
Preheat oven to 350 degrees. Line a large roasting pan with foil; fit roasting rack inside. Place ham, flat side down, on a large piece of parchment or waxed paper. With a sharp paring knife, lightly score layer of fat on top of ham in a diamond pattern (do not cut into meat). Combine sugars.
Evenly brush top of ham with mustard. Press sugars onto mustard to coat evenly.
Place on roasting rack, coated side up. Roast until warm throughout, about 1 hour. Raise heat to 450 degrees; roast until crust is crunchy, about 15 minutes more.