Melt the butter. Put flour, 250 g sugar, vanillin sugar, salt, 60 g pistachios and half of the orange peel in a bowl. Add butter. First use the dough hooks of the hand mixer, then work it into a smooth dough with your hands. Divide into 4 pieces of equal size and form a roll (3 cm Ø) each. Wrap in foil and chill for approx. 3 hours
Mix 100 g sugar and 25 g pistachios. Mix the remaining orange peel with another 100 g of sugar. Whisk egg yolk and 1 tbsp. water. Brush dough rolls with egg yolk all around. Roll 2 rolls each in the pistachio sugar, the other two in the orange sugar. Cut into slices (approx. 8 mm thick)
Place on 4 baking trays lined with baking paper, leaving a space between them, as the cookies will run slightly apart. Bake the trays one after the other in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 10-12 minutes. Take out and let cool down
waiting time approx. 3 hours