For the Karlsbader Ringerln, mix all ingredients and quickly knead into a smooth dough. Wrap the dough in cling film and refrigerate for two hours.
Preheat the oven to 170° C.
Roll out the dough on a floured work surface and cut out discs. Cut out a hole from the center of the discs.
Place the cookies on a baking sheet lined with parchment paper and brush the rings with the egg yolk and milk mixture.
Sprinkle hail sugar on the Karlsbader Ringerln and bake for about 12 minutes.