Crumble the yeast and dissolve in 800 ml lukewarm water while stirring. Put salt, caraway, both types of flour, sourdough and sugar in a large bowl. Add yeast water and knead everything into a smooth dough. This is best done with a food processor or with your hands. Cover the bowl with a damp tea towel. Let the dough rise in a warm place for about 1 hour until it has doubled in volume.
3 Line baking trays with baking paper. Briefly knead the dough on a floured work surface, divide into approx. 15 pieces. Form each piece into a round shape and press flat. Spread on baking trays and dust with flour. Cover and let rise again for about 10 minutes. Bake in the preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: see manufacturer) one after the other for approx. 25 minutes. Remove and let cool on a cake rack.