Make a light batter with the above ingredients, beating well, and let it stand for about 1 hour. Put a very small piece of butter in a small frying pan and, when it has melted and the whole pan is coated, remove the pan from the fire, and quickly pour a little of the batter in the pan, tilting it from side to side so that it spreads evenly and thinly, covering all the pan. Replace at once on the fire, and when one side is done, either toss the pancake or turn it carefully with a fork. When done, remove from the pan. Let the pancakes get cold, then cut them into very thin strips—almost as fine as vermicelli—and add to the soup just before serving.