Brush ham steaks with melted butter. Snip fat to prevent curling, and grill for 7-8 minutes each side.
Sauté onions in remainder of butter until cooked. Remove from heat and stir in flour gradually. Add water or stock. Return to heat. Add sugar and bring to the boil. Simmer gently for about 2 minutes to cook flour. If sauce seems a little thick, add more water or stock. Add whiskey and season to taste. Place ham steaks on a serving platter and pour on sauce.