Fluffy Sponge Cake
["6 eggs, separated", "1 1/2 c. sugar", "6 Tbsp. cold water", "1 1/2 c. flour (plain)", "1/4 tsp. salt", "1 1/2 tsp. baking powder", "1 tsp. vanilla"]
["Beat egg yolks until thick.", "Add sugar and beat until smooth. Add flour and water, alternately, beating constantly.", "Add vanilla."]
["eggs", "sugar", "cold water", "flour", "salt", "baking powder", "vanilla"]