Heat oven to 425 degrees.  In a bowl, beat eggs very lightly and add sugar gradually.  Add water and continue lightly beating.  In a sifter combine flour, cocoa, baking powder, and salt.  Sift these ingredients into the egg mixture.  Add vanilla and mix.

           

Line a 10×15 cookie sheet (you can use bigger baking sheet, but the cake will be thinner and you need to shorten baking time) with dull side of foil or wax paper.  Grease the foil or wax paper.  Pour cake mixture into baking sheet.  Bake for 11-14 minutes.

    

While cake is baking, you will need to take a clean kitchen towel and lay it flat on the countertop.  Dust the entire surface of the towel with confectioners sugar.  When the cake is finished baking, you will immediately turn over the baking sheet onto the towel.  The cake will be dumped onto the towel (onto the sugar).  Remove the foil or wax paper.  Now LOOSELY roll the cake up in the towel.  Let the cake cool for about an hour or two.

     

After the cake has cooled, unroll it.  Get out your completely frozen ice cream.  DO NOT THAW your ice cream.  The best way to do this is to buy the ice cream that is in a brick shaped container.  I know they are getting harder to come by, but trust me, it makes a world of difference! 

Completely open the quart of ice cream, so that it is just one big block sitting there with no sides or top to it.  Using a large knife, slice the ice cream.  Place the slices onto your cake.  Leave a little space in between the slices.  Now roll up your cake, cover with foil, and put it back in the freezer.  Try to let it freeze for a few hours before serving.  It tastes best when the cake is frozen, too. 

When you are ready to serve, just slice and eat.