Coarsely chop the dark chocolate. Melt butter and dark chocolate in a bowl over a warm water bath.
Mix flour, baking powder and cocoa well in a bowl. In another bowl, beat the sugar, vanilla sugar and eggs for approx. 5 minutes with the whisk of the hand mixer until creamy. Add the chocolate-butter mix. Alternate the flour mixture and milk in portions and also fold into the mixture.
Pour the dough into a round springform pan lined with baking parchment (approx. 26 cm Ø), distribute evenly and smooth down. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 25-30 minutes. Stick test!
Remove the cake from the oven and let it cool down briefly. Remove from the mould and allow to cool completely on a cake rack.
In a tall container, whip cream until stiff with the whisks of the hand mixer. Let the icing sugar trickle in. Spread the cream on the cake and smooth it down. Spread chocolate drops as a football pattern on the cake.