I have made this for my family for over 40 years. When my kids were small and I was making this for company, I had to make two of them..one for company and one for my kids..they always requested this chocolate roll when asked what they wanted for desert.
Beat egg yolks until lemon colored. Sift together 3 TBSP cocoa and 1 cup confectioners sugar. Add egg yolks and blend until smooth. Add 1 tsp vanilla. Fold into stiffly beaten egg whites until blended.
Pour into well greased and floured cookie sheet (approx. 10: x 15". Bake in preheated 375 degree oven for 10 - 15 minutes. Meanwhile, dampen a kitchen towel and lay out on counter. Sprinkle with confectioners sugar (using a sifter) using about 1/2 cup sugar. Turn cookie sheet upside down on dampened towel so cake is on top of the sprinkled sugar. Gradually lift the cookie sheet from the cake (I use a spatula being careful not to break it up). Start rolling the cake into a 10" roll so that it is inside the towel. Sit aside to cool.
When the roll is cool, carefully unroll it and spread it with the cool whip (you can also make your own whipping cream. Then carefully roll it back up and sit it on an attractive platter with the smooth part facing up. Frost it by mixing 3 TBSP cocoa and 1 - 1 1/2 cups confectioners sugar mixed with just enough milk to make it easy to spread. Probably no more than 2 or 3 TBSP milk. Spread all over including the sides. Keep refrigerated until ready to serv. Cut into slices.