For the poppy seed crescents, knead the flour, powdered sugar, dry yeast, salt, vanilla sugar, finely chopped butter, yolks and milk in a food processor for at least 10 minutes and leave to rest.
For the filling, boil the milk together with the powdered sugar and the honey, then add the poppy seeds and let them swell a bit over low heat.
Roll out the dough and cut out 9 squares. Put some filling on one side and brush the other side with beaten egg, roll up and brush the finished croissant with egg again.
Bake in the oven at 180 degrees for about 15 minutes.