Grease a 9 X 13 pan. In a large bowl, beat egg whites until soft peaks form. slowly stir in sugar and continue beating until peaks start to harden. In a clean bowl, beat egg yolks until fluffy and creamy in color. Stir in 1 tablespoon vanilla and beat for 1 minute. Gently mix together yolk and egg white until uniform. Fold in flour, mix until well combined. In a small bowl, combine hot water with cocoa powder. Pour half the cake batter into another bowl and fold in the cocoa mixture.
Spread the vanilla batter in the baking pan. Pour chocolate batter in a straight line over the top. With a knife, making a whirling design. Bake for 22-25 minutes. Remove from oven and let cool.
Poke holes around cake with a fork, In a clean bowl, combine milks with 1 tablespoon vanilla. Pour sauce over cake.
Whip heavy cream and powder sugar until the mixture peaks. Spread over top the cake. Garnish with grated chocolate. Refrigerate