Cut the vanilla pod lengthwise and scrape out the pulp. Put flour, sugar, vanilla pulp and salt on a work surface, make a depression in the middle, add egg and spread fat in flakes on the rim. Knead the ingredients with your hands to a smooth dough. Divide the dough into thirds and form 3 rolls (approx. 25 cm long). Use a ruler to form triangles from the rolls. Leave to cool well for approx. 45 minutes.
Whisk the egg white with a fork. Mix vanillin sugar and decorating sugar. First brush the triangular rolls with whisked egg white and then turn them into sugar crystals. Cut approx. 25 slices from each triangular roll, place on three baking trays lined with baking paper and bake in the preheated oven (electric range: 175 °C/ gas: level 2) one after the other for approx. 15 minutes. Remove the cookies from the oven and let them cool down on a grid. Results in approx. 75 pieces