Preheat the oven to 180 degrees top and bottom heat.
Put the butter in a bowl and stir with the mixer until smooth. Gradually add the sifted powdered sugar with the vanilla sugar, flavoring and salt while stirring until a thickened mass is formed. Briefly stir in the sifted flour and poppy seed baking alternately in 2 portions on the lowest setting.
Pour the dough in portions into a piping bag with an 8 mm perforated nozzle and squirt dots onto the baking sheet lined with baking paper. Bake for 10-12 minutes. Attention! If you make relatively small spots, you should check after 7 - 8 minutes so that they don`t get too dark!
Remove the pastries from the baking sheet with the baking paper and leave to cool on a wire rack.
For the filling, strain the jam through a sieve. Spread the jam on half of the cookies on the underside and place a second cookie on top of each one and press lightly.
Melt the white couverture in a water bath and dip one side of the biscuits into it. Let it set on baking paper.