Dissolve the yeast in the 170 ml water and mix with 150 g whole wheat flour. Cover this pre-dough and place it in the refrigerator for about 12 to 24 hours (preferably overnight). Let the pre-dough stand for 1 hour at room temperature before further processing and then stir in or knead in the remaining ingredients. Let the dough rest for about 1/2 hour, then knead or fold again briefly and form a loaf of bread from it. Let it rise in a proving basket for about 1.5 hours, then turn it out onto a baking sheet lined with baking paper and cut into it. In the meantime, heat the oven to 260 ° C, make sure that there is steam and then pour in the bread. After 10 minutes, lower the temperature to 230 ° C and switch it down to 200 ° C after a further 10 minutes. After another 10 minutes, turn it down to 180 ° C and bake for about another 15 minutes - a total of about 45 minutes baking time.