Put the sourdough in a bowl and add the water and stir until smooth. Add the flour and rye and stir smoothly. Clean the edges and put the edges covered away at room temperature, 12-2 hours.

Put all the ingredients including the levain in a standing mixer with dough hook. Leave to rest for 15 minutes when the dough creeps up against the dough hook and becomes detached from the wall of the bowl. Then mix in middle class for another 5 minutes until the dough is nicely smooth. If it's too sticky, add some flour. Grease a bowl with oil and roll the dough around in, cover and rise to the double volume, about 3 to 4 hours.

Place the dough on a floured worktop. Press gently flat, so that the large air bells can escape. Make a rectangle of 28 x 23 cm and fold in threes, cover and leave to rest for 45 minutes. Turn the dough a quarter stroke, fold in threes and leave to rest for 30 minutes.

Fold the dough in half and form a round bread from it by placing the edges underneath creating a smooth surface. Place the dough with the seam down with flour pollinated baking paper on a baking sheet and pollinate with flour. With a sharp knife, make a 4 cm cross in the middle and four smaller notches towards the outer edge. The notches must be 2.5 cm deep, so pretty deep. Cover and leave for another 2 hours, until the volume is doubled.

Preheat the oven to 250ºC and place a baking sheet in it. When the oven is at temperature, slide the dough with baking paper and all on the hot baking sheet and pollinate the oven with some water. Bake for 10 minutes at 250ºC and then 20 minutes on 200ºC. Bake golden brown and the bottom hollow sounds.