Mix all the ingredients thoroughly in a bowl. Allow to stand for at least 3 hours. Butter some heated wafer irons (these are not waffle irons), by rubbing them with a small knob of butter wrapped in a piece of muslin. Pour 1 tablespoon of the batter on to the lower plate of the irons and close the upper plate tight. Cook the wafer on both sides for a few minutes over hot charcoal or over a low gas flame. When cooked, remove carefully from the irons.