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 2 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.