For grandma’s vanilla crescents, prepare the vanilla sugar for rolling at least 24 hours in advance: To do this, slice the vanilla bean lengthwise and place in a tightly-sealing tin together with 500 g of powdered sugar.
For the croissants, heap flour on the work surface. Flake cold butter into the flour, crumble and form a hollow. Add yolks, sugar, vanilla sugar, salt and hazelnuts and knead into a smooth shortcrust pastry. Refrigerate the dough for a few hours (preferably overnight).
Either form small croissants by hand or form rolls with the piping pastry attachment of the food processor, cut them into suitable pieces with a knife and bend them into croissants. Place the croissants on a baking tray lined with baking paper and bake at 160 °C hot air until light blond.
Immediately roll the finished vanilla crescents from grandma in vanilla sugar.