Grease the springform pan (24 cm Ø). Separate the eggs, beat the egg white and 3 tbsp. water until stiff, pouring in 125 g sugar. Stir in egg yolks one after the other with a whisk. Mix flour, starch, baking powder and 20 g cocoa, sieve onto the egg mixture and fold in.
Fill the sponge mixture into the mould and smooth it down. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 35 minutes. Let cool down on a cake rack. Cut the sponge cake in half horizontally
Whip the cream until stiff, then pour in 20 g sugar. Stir cranberries until smooth. Spread the lower sponge cake base with cream, spread cranberries evenly on top. Place the second sponge cake base on top. Sift icing sugar first, then 10 g cocoa powder over the cake