Cake: Preheat the oven to 180 degrees C. Line a baking tray with baking paper.
Beat the sugar and butter together, add egg yolks, sour cream, baking powder and vanilla sugar. Mix well and divide into two equal parts.
In the first half mix in 125g flour. In the second mix remaining 75g flour and cocoa.
Beat the egg whites until stiff, divide into two and mix gently into the two batters.
In the centre of the prepared baking tray place two tablespoons of the plain batter. In the centre of that, place two tablespoons of the chocolate batter. Continue, adding alternating layers of batters to form a cake.
Bake for 45 minutes in the preheated oven.
To Arrange: When the cakes are cool, cut into two unequal halves horizontally, leaving the bottom half about 15ml high. Cut the top half into cubes. Sprinkle the reserved cherry juice over the lower half.
Sprinkle the cherries with icing sugar. Whip the cream with sugar. Put a layer of whipped cream over the bottom half of the cake and evenly distribute half the cherries and half the nuts.
Dip the cubes of cake in remaining whipped cream and pile up on the bottom half of the cake to form a dome. Decorate with remaining cherries and nuts.