Japanese Very Light Tempura Batter

Ingredients

 * 1 egg  
 * 1 cup very very cold water 
 * 1/8 teaspoon baking soda  
 * 3/4 cup all-purpose flour or tempura flour (3 oz)

Directions
Break the egg into a bowl containing the iced water and whisk until frothy.  Add baking soda and flour.  Beat until the flour is just mixed in.  Do not over beat.  Batter should be so thin that the merest wisp clings to the vegetables dipped in it.  If it seems too thick, add a little more iced water, and keep the batter cold.