Schüttelbrot - Chrunchy flat bread

Sourdough starter:
Dissolve the yeast in lukewarm water, add to the flour, mix well to produce a soft dough, cover and leave to leaven in a warm place (30 °C) for 1 hour.
Completion:
Mix the sourdough with the remaining ingredients to produce a uniform dough, cover and leave to rest for 10-15 min. Divide the dough into 10 pieces of similar size (150 g), form into rolls and place onto cloths dusted with flour. Leave to rise for 10 min. The bread is called Schüttelbrot because it is shaken flat. Place each roll onto a board the size of a pizza and shake, turning the board and causing the rolls to broaden until they are finally flat. Bake at 210-220 °C for approx. 30 min.