Mix the two flours in a mixing bowl and make a well. Dissolve the yeast in the buttermilk and then pour it into the well. Add the remaining ingredients and knead with the dough hook on the highest setting for about 3 minutes to form a smooth dough. Let the dough rise covered for 20 minutes (warm up the oven to 50 ° C, switch it off and let the dough rise there covered.)
Then knead again briefly by hand.
Shape the dough into a firm ball on baking paper, flour a little and place on a baking sheet with the baking paper. Heat the oven again to 50 ° C, switch off, then cover the dough ball and let it rise for another 20 minutes until the dough has enlarged significantly. Then cut into the blank in a grid shape 1 cm deep.
Heat up the oven, bake on the middle rack:
Electric stove: 10 min. 250 ° C, then 30 min. 200 ° C
Hot air: 10 min. 200 ° C, then 30 min. 170 ° C
Gas stove: 10 min. Setting 4-6, then 30 min. Setting 2-3