Mix the butter, sugar and vanilla sugar until frothy. Gradually add the eggs and stir the mixture well. Mix in the flour and cocoa. Preheat the oven to 160 ° C.
Place small heaps of the dough with two teaspoons on a baking sheet lined with baking paper, but leave some space because the cookies will run apart. Bake for about 15 minutes.
Glue two biscuits together with currant jam while they are still warm.