For the dough mix yeast and 1 tablespoon of sugar until the yeast becomes liquid. Heat 200 ml milk. Knead 500 g flour, 75 g sugar, 1 pinch of salt, egg, yeast and milk with the dough hooks of the mixer, kneading 50 g soft butter in flakes until the dough is smooth.
If it forms a ball, continue kneading for about 3 minutes. Cover the dough ball and leave to rise in a warm place for about 1 hour. Grease a box form (approx. 15 x 35 cm) and dust with flour.
Briefly knead the dough onto some flour and roll out into a rectangle (approx. 30 x 50 cm). Halve lengthwise. Spread the groats on both halves, leaving about 2 cm free all around. Roll up from the long side of each half.
Twist the dough rolls together and place in the form. Cover and leave to rise for about 30 minutes.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Brush the yeast whirl with 2 tablespoons of milk and sprinkle with coarse sugar. Bake in the hot oven for approx. 40 minutes, covering with foil after 30 minutes if necessary.
Take out, let it cool down for about 30 minutes and carefully lift it out of the mould. Let it cool down.