For the dough, first beat the butter, sugar and vanilla sugar until frothy. Then add flour and cornstarch and stir in. Finally add the almonds, 1 tablespoon rum and cocoa and work into a smooth dough. Let rest in the refrigerator for about half an hour.
Then shape into small (half) balls and bake at approx. 180 ° C for about 8-10 minutes.
When the balls have cooled down, make a frosting from powdered sugar and 2 tablespoons of rum, spread over the biscuits and allow to dry.