For the dough mix yeast and 1 teaspoon sugar until the yeast is liquid. Warm the milk lukewarm. Knead flour, 75 g sugar, salt, egg, butter, yeast and milk to a smooth dough. Cover the dough and leave to rise in a warm place for at least 1 hour.
In the meantime, for the groats, select the berries, clean and possibly wash them. Strip the currants from the panicles. Boil up the cranberry nectar to about 50 ml. Stir sauce powder, remaining nectar and 4 tbsp. sugar until smooth and bind boiling nectar with it.
Bring to the boil again and simmer for about 1 minute. Remove the pot from the heat and stir in the fruit.
Roll out the dough into a rectangle (approx. 30 x 50 cm) on a floured work surface. Halve lengthwise. Spread the groats evenly on the dough halves, leaving about 2 cm free at each side.
Roll up the dough halves from one long side each. Twist the dough rolls together so that the cord is about 30 cm long. Place in a greased and flour-spread box form (approx. 11 x 32 cm).
Cover again and leave to rise for about 30 minutes in a warm place.
Whisk with egg yolk, brush the dough with it and sprinkle with coarse sugar. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 40 minutes. If necessary, cover with foil about 15 minutes before the end of the baking time.
Remove from the oven and leave to cool on a cake rack. Remove from the mould and allow to cool. Arrange and cut into slices.