Make a kneading dough from flour, baking powder, butter, sour cream and salt. Chill it for 1 hour.
Then roll out ½ cm thick and cut out round cookies or rings. Place on a baking sheet. Whisk egg yolks with milk and then brush with them. Finally, sprinkle thickly with the sugar.
Bake in a preheated oven at 180 ° C for approx. 10-15 minutes.