Remove rind and trim off all but 1/4-inch of outer fat. Cut ham into two serving pieces. Score the fat edge at 1-inch intervals so the steak does not curl during cooking. Lightly saute, ham on both sides in butter for 3 to 4 minutes a side. Remove ham steak to a plate.
Add apple and saute until somewhat soft. Stir in mustard and cider and reduce until the cider has almost entirely evaporated. Add the heavy cream and reduce until slightly thickened. Season to taste with salt and pepper and spoon sauce over steak.