Crumble the yeast and dissolve it in the buttermilk. Put the flour and salt in a bowl, add the buttermilk and knead thoroughly. Let rise overnight in a cool place (refrigerator, balcony in winter). The next morning, preheat the oven to 200 degrees. Knead the dough again, divide it into 10 equal pieces, make a cross with a knife and brush with milk. Place on a baking sheet lined with baking paper and bake on the middle rack for about 30 minutes until the rolls are golden yellow. If you like, you can sprinkle them with poppy seeds, sesame seeds, sunflower seeds or the like before baking or knead them into the dough.