Beat egg yolks for 3 minutes, add 1/2 cup sugar and beat 2 minutes more.
In a separate bowl, combine flour, cocoa, 1/4 cup sugar, baking soda, and salt. Add the dry ingredients alternately with the water to the egg mixture. Stir in vanilla.
In another bowl, beat egg whites until soft peaks form; add 1 tablespoon of sugar and beat until stiff. Fold mixture into the batter. Cover the bottom and sides of a jelly roll pan with wax paper. Grease wax paper completely with Crisco. Spread batter into pan and bake at 375 degrees for 15 minutes or until top springs back when touched.
Sprinkle powdered sugar on a towel the size of the jelly roll pan. While the cake is still hot, turn onto towel, peel off wax paper and roll gently with towel and cool. Unroll, spread a layer of ice cream, then roll again. Wrap in heavy-duty foil and freeze 3 hours.
