For the vanilla crescents, crumble the flour with the butter. Add the yolks, hazelnuts and sugar and quickly knead into a shortcrust pastry.
Leave to rest in the refrigerator for 1/2 hour. Shape into croissants and place on a baking tray covered with baking paper. Bake at 180 degrees in the oven.
Turn the croissants in powdered sugar with vanilla sugar.