Mix the sourdough with flour and water and let rise at room temperature for 16-24 hours covered with cling film. Then remove 50 g of it for the next sourdough.
Add the remaining ingredients to the sourdough and mix slowly with the food processor for 10 minutes, cover with cling film and leave to rest for 30 minutes.
Then cut the dough in half and work it on a little flour and grind long or round, depending on the bread shape. Covered in a proofing basket sprinkled with flour (in a plastic bag with 6 l content), let rise for 2-3 hours and turn over onto a baking sheet lined with permanent foil. Cut the dough several times on the top and on the side.
Bake in the preheated oven at 250 ° on the second rack from the bottom for 10 minutes, switch the temperature down to 190 ° and bake for another 35-45 minutes (do a tapping test).