In a bowl, mix together half of the flour and half of the water, cover with a cloth and allow to rest for 1 hour at room temperature (autolysis).
Add the salt, the yeast, the remaining flour and water and the sourdough starter, then knead with an electric mixer using the dough hook for 10 minutes on minimal speed, and then for 30 seconds on medium speed.
Divide the dough in two balls. You can add to one of the dough balls : 25 g of pumpkin seeds, 25 g of sunflower seeds and 25 g of flax seeds (that were marinated for 2 hours in 75 g of water).
Place the two balls in two bowls covered with a cloth, and allow to rest for 1 hour at room temperature.
Line the inside of your mold with baking paper. Shape two balls and place them in two GEOFORME molds, cover with a cloth and allow to rest for 12 hours at 4 °C (39 °F), in the fridge.
Cover with a cloth and allow to rise for 1 hour 30 minutes at room temperature.
Preheat oven at 250 °C (480 °F),
Score the dough and, if desired, add a little bit of flour.
Bake for 20 minutes at 250 °C (480 °F), then for 10 minutes at 180 °C (355 °F). Open the molds and allow to cool.
Start making your sourdough starter 5 days before making the bread, as follows:
Mix 20 g of whole-wheat flour, 20 g of water and 5 g of honey.
Whisk well, pour in a glass jar, cover with a clean cloth and leave at room temperature.
Mix 40 g of whole-wheat flour, 40 g of water and 5 g of honey. Combine with the mixture from day 1, using a larger container. Cover with a clean cloth and leave at room temperature.
Mix 80 g of whole-wheat flour with 80 g of water and combine with the mixture from day 2. Cover with a clean cloth and leave at room temperature.
Mix 100 g of flour with 100 g of water and combine with the mixture from day 3. Split in two and place in two jars. Cover both jars and allow to rest for 24 hours at room temperature.
On the day you make the bread, divide the sourdough starter in two again, add 50 g of water and 50 g of flour to each, and place one in the fridge. You might need to “feed” it (don’t spend more than 5 days without maintaining it), or give it to someone. According to French tradition, you’re also supposed to name it! Leave the other one at room temperature and use it to make your bread.
Trained as a Chef and titled “Meilleur Ouvrier de France” in 2011, Fabien Pairon worked in France and abroad in various gastronomic outlets before joining EHL.