Foto: Kurt-Michael Westermann
Combine the flour, icing sugar, ground walnuts and salt, and heap onto a baking tray.Make a shallow hole in the middle and beat in the egg yolk. Place small pieces of butter around the edge of the flour. Cut them into smaller pieces and, then with cold hands, quickly knead the mass into a smooth dough.
(It is quicker and easier to use a blender). Shape the dough into a ball and cover with plastic wrap. Refrigerate for about 30 minutes. Preheat the oven to 170 °C. Form small, finger-width rolls out of the dough and cut pieces about 1 cmthick fromthem. Roll into small balls and, on a lightly-floured surface, shape into crescents. Place on a baking tray lined with baking paper and bake for 12–15 minutes.
Loosen the crescents from the paper with a spatula, allow to cool, then toss them in the vanilla icing sugar. Allow to cool on a cake grid and then put into a cookie tin.