For the mini chocolate sponge cake, first separate the eggs. Beat the egg whites until firm. Preheat the oven to 180 °C. Mix the yolks well, then add the butter and continue mixing.
Then add sugar, vanilla sugar, sour cream and finally the cocoa and continue mixing. Mix the flour with the baking powder, then add to the yolk mixture alternately with the beaten egg whites.
Pour the cocoa mixture into the mini silicone muffins and bake at 180 °C top and bottom heat for about 30 minutes.
Allow to cool, garnish with whipped cream and powdered sugar and serve.