Preparation time: 60 min. Baking time:15 min.
Peel cold potatoes, grate finely. Knead together with sugar, egg, butter, baking powder, salt, flour, vanilla pulp and lemon zest until smooth. Chill dough for half an hour.
Preheat electric stove to 175 °C. Cover the baking tray with parchment paper.
Roll out the dough to a thickness of about 3 mm, cut out circles (6 cm ø).
Brush a little bit of Powidl on each circle, leaving about 1 cm free at the edge. Fold up circles on three sides. Press the sides of the dough firmly together to form a tricorn.
Mix egg yolk with milk. Brush the cookies with the mixture and sprinkle with hail sugar. Bake in the oven at 175 degrees (gas: level 2) for about 15 minutes until golden brown.