Remove rind and trim off all but 1/4-inch of outer fat. Score the fat edge at 1-inch intervals so the steak does not curl during cooking and divide ham steak into serving pieces. Marinate ham in soy sauce and sherry wine. Remove ham from marinade. Reserve marinade. Dry the ham steak and lightly brown in butter for a minute or 2 on both sides. Add ginger, water and reserved marinade to the skillet and bring to a boil. Cover and cook for 5 minutes or until heated through. Remove ham to a serving platter. Boil the liquid down until syrupy and season to taste with salt and pepper. Stir in the scallions and spoon sauce over steak.