For the sour cream rings, sift the flour with starch, add soft butter and sour cream and knead everything into a smooth dough.
Wrap in plastic wrap and let rest for at least 1 hour. Roll out the dough to a thickness of approx. 3 mm, cut out rings with a diameter of approx. 3-4 cm, brush with the yolk whisked with milk and sprinkle thickly with hail sugar (place the coated rings upside down on the hail sugar on a plate and press lightly).
Bake for approx. 15 minutes at 200 °C top/bottom heat until light brown.