1. Brown the ground almonds in a hot frying pan, then leave to cool. Quickly knead the butter, icing sugar, egg yolk, vanilla pulp, flour, almonds and salt by hand to make a smooth dough. Stand the dough in a cold place for 2 hours.
2. Shape about 30 croissants from the dough and place them on a baking tray lined with a Filou Flexx magic sheet. Cook in a preheated oven at 200°C for about 10 minutes.
3. While the croissants are still warm, roll them in the vanilla icing sugar. The previous day, the two scraped out vanilla pods must be mixed with the icing sugar and stored in a tightly sealed jar. The vanilla flavour will then permeate the icing sugar. Place the vanilla croissants in layers in a biscuit tin, with a sheet of greaseproof paper between each layer.