make the dough
Add hazelnuts, walnuts, all-purpose flour, and a pinch of salt to a bowl. Stir to combine. Cut the butter into cubes and add to a separate bowl. Add the powdered sugar and vanilla sugar to the butter and mix with an electric mixer fitted with the dough attachment or knead in a stand mixer fitted with a dough hook. Mix until just combined, not whipped. Add the dry ingredients and stir to combine, then knead into a smooth dough with your hands. Place the dough back in the bowl, cover it with clingfilm, and place it in the fridge for one hour.
Line a large baking sheet with parchment paper. Place a rack in the middle of the oven and preheat it to 190 °C / 375 °F. Add powdered sugar and vanilla sugar to a small bowl. Stir and set aside. This is your coating.
Take the dough from the fridge. Scoop a teaspoon (10g) of butter from the dough and shape it into a round ball. Then, shape it into a rope on your lightly dusted working surface. Shape into a crescent cookie. Place each cookie on the prepared baking sheet. Repeat the process until you get about 60 cookies. Leave enough space between them when baking.
Place the cooking in the oven and bake for 13 – 15 minutes at 190 °C / 375 °F or until they are golden brown. When baked, take them from the oven, set them aside to cool, and then generously dust them with vanilla powdered sugar.