Knead the flour, sugar, almonds, butter, egg yolks, speculoos spice, 1 packet of vanilla sugar and salt to form a smooth dough. Cover and chill for approx. 1 hour.
Preheat oven.
Shape the dough into small, approx. 6 cm long strands and bend them into croissants. Place the croissants on a baking sheet lined with baking paper and bake on the middle shelf for 13-18 minutes at 175 degrees.
Prepare a mixture of powdered sugar, 2 packets of vanilla sugar and cinnamon and carefully turn the croissants in it while they are still warm.
The cooled speculoos biscuits can be stored in airtight containers.