Knead all the ingredients for the dough into a smooth dough. Wrap in cling film and put in the freezer for about 30 minutes. Grind the walnuts finely and mix with the two sugars. Divide the dough into 3 parts and roll out to a circle, using the walnut-sugar mixture as a flour substitute.
Sprinkle the rolled out dough with the walnut - sugar mixture and divide into 16 cake pieces. Roll the dough pieces into croissants from the broad side and live them on a baking tray covered with baking paper.
Bake in a preheated oven at 180°C for about 25 minutes.