Preheat oven to 360 degrees (circulating air 320 degrees).
Grease a small baking tray or line it with baking paper.
Coarsely chop the dark chocolate and melt with the butter in a bain-marie.
Let cool down briefly.
Mix the butter chocolate mass with the sugar, gradually add the eggs and stir.
Mix flour, salt and cocoa powder and add to the remaining dough and mix together.
For the cheesecake mass, briefly mix the cream cheese, egg, powdered sugar and vanilla sugar.
Put two thirds of the brownie dough into the form and smooth it down.
Pour the complete cheesecake mixture onto the dough and spread evenly.
Spread the rest of the brownie dough in blobs on the cheesecake mixture and marble lightly with a fork or wooden skewer.
Bake the brownies in a preheated oven for about 30 minutes.
Leave everything to cool down and enjoy.