Grandma Sumida's Watercress Tempura
½ cup less 1 Tbsp. Cornstarch
½ cup plus 1 Tbsp. Flour
1 tsp. Salt
1 bunch Sumida Watercress
Beat egg thoroughly with a fork. Pour egg into a measuring cup and add enough water to measure a total of ¾ cup. In a bowl, combine dry ingredients and mix well. Pour egg mixture into dry ingredients and mix well by folding. Do not beat; the little lumps do not matter.
For best results, chill the batter in the refrigerator for at least one hour before using. Wash watercress, drain and cut into one inch pieces. Put watercress into batter and mix well. Drop this mixture by tablespoons and fry in very hot, deep oil until golden brown and crunchy.