Put the flour, almonds, hazelnuts, sugar, 1 packet of vanillin sugar, salt and egg yolks in a bowl. Add butter in pieces. Knead first with the dough hooks of the hand mixer, then briefly with your hands to a smooth dough. Form into a ball, wrap in foil and chill for approx. 1 hour
Gradually form small pieces of dough on the work surface into 1-1.5 cm thick rolls and cut them into 4-5 cm long pieces. Roll individual pieces a little thinner at the ends and form into croissants. Place on two baking trays lined with baking paper and bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for approx. 10 minutes one after the other, so that the tips in particular become brown
Sift the icing sugar and mix with 4 sachets of vanillin sugar and bourbon vanilla sugar. Carefully roll hot croissants in it. Let them cool down on a cake rack. Keep the croissants well closed in tins in a cool place. Keep for about 4 weeks.
Waiting time approx. 1 hour