Line the bottom of a springform pan (26 cm Ø) with baking paper. Melt butter at low heat. Separate the eggs. Beat the egg whites and 1 pinch of salt until stiff, adding 125 g sugar. Fold in the egg yolks one by one.
Sift flour, cocoa and baking powder on top and fold in. Fold in liquid butter.
Pour the mixture into the mould and bake in a preheated oven (electric oven: 175 °C/circulating air: 150 °C/gas: see manufacturer) for 15-20 minutes. Let the base cool down on a cake rack.
Stir cream cheese, mascarpone and vanilla sugar until smooth. Stir in icing sugar and cranberries briefly. Put them in a cold place.
Cut out 12 circles (approx. 5 cm Ø) from the sponge cake base (use the leftovers for other purposes). Pour cranberry cream into a piping bag with a large spout and squirt it about 2 cm thick onto 6 circles.
Place the remaining sponge cake circles on top and decorate with the remaining cream.