1 egg
½ cup cold water
¾ cup flour
¼ cup cornstarch

Just before using, beat egg with cold water until light. Stir together flour and cornstarch, then sift into mixture. Mix lightly and quickly with as few strokes as possible to keep batter light.

A batter with a few lumps remaining is OK. If needed, thin batter with a little additional water until it has the consistency of light cream.