To prepare the dough, dilute the raw yeast and 2 tsp sugar in warm water until completely dissolved. Add a little flour and stir. If the yeast is active, bubbles will appear after a short time, you can knead the dough. Add warm milk, salt, remaining sugar, sour cream, mix well, add sifted flour, knead the dough with a spoon. Add the melted butter. Mix again.