Mix the flour, sugar and poppy seeds on the work surface and form a well in it. Put the diced, cold butter and the egg yolk in the hollow and knead well.
Wrap the dough in aluminum foil or cling film and place in the refrigerator for at least an hour. Knead the dough well after an hour, roll out and cut out with molds.
Bake the biscuits in the preheated oven on a baking sheet lined with baking paper at 180 degrees top / bottom heat for about 10 minutes.
Then let it cool down, then brush with Powidl and put it together.