SOURDOUGH & POOLISH PREP: Mix the ingredients for the sourdough and poolish dough in separate bowls. Let the rest for 12-15 hours at room temperature. The poolish dough will get bubbly like the photo here...

And the sourdough will get soft and kind of frothy like this photo.

WHEAT BERRIES: Prepare the cooked wheat berries: bring 100 g to a boil in 150 g (= 150 ml) water. Cover with lid, turn to lower heat and let cook for 10 minutes. Remove lid and cook until any residual water is gone. Let cool completely (I like to do this step ahead of time so I don't need to worry about when I'm ready to knead and bake).

MIX AND KNEAD: When the sourdough and poolish are ready, mix them together with all the other dry ingredients (except flax seeds). Add enough water or beer to form a kneadable dough (you don't want it super sticky).

Knead for 15 minutes until the dough is smooth and elastic. Dust hands or kneading surface with additional flour if the dough is sticking too much.

After 15 minutes, fold in the flaxseed if using and knead for 1 minute.

FIRST RISE: Form into a ball and place in a bowl to rise for 1 hour at room temperature. Cover it with plastic wrap so it doesn't dry out. After 1 hour, re-fold into a ball and let rise another 20-30 minutes.

FINAL RISE: Remove from bowl and re-fold into a ball or oblong loaf (whatever shape you want the final bread to be.）

Dust with rye flour and let rise in a floured banneton or basket lined with a bakers linen (fold/crease facing up) for 45-60 minutes. If you don't have the banneton or basket, let it rise (fold/crease facing down) on the a parchment paper lined baking sheet cover with a tea towel.

OVEN & STEAM PREP: During the final rise, preheat the oven to 250°C/480°F. Place a shallow oven-safe pan at the bottom of the oven while preheating - you'll use this to create steam later! (You can skip the steam if necessary, but this is what gives the bread crust a nice color and makes it crisp).

When the dough has finished it's final rise, place on the baking sheet with the crease facing bottom (unless you already did this). Cut slits into the dough in whatever pattern you like.

Bake for 10 minutes at 250°C/480°F, then remove the steam pan. Lower the heat to 220°C/430°F and bake for another 30 minutes. Remove from oven and let cool uncovered on a wire rack.