Around 7:30 am (or whenever you wake up) mix the levain by combining all the ingredients and stir it. Loosely cover the levain and leave it somewhere warm for about 5 hours until you see bubbles.
Around 1 pm mix together the whole wheat flour, bread flour, water, and levain. You should have quite a shaggy mess at this point. Don’t worry it will smooth out later on. Cover the mess lightly and leave it somewhere warm for an hour.
For the second mix add the salt and the last bit of water (1 tsp or 5 g) and mix it together by stretching and folding the dough for 3 or 4 minutes until the salt is mixed in.
Now we’re going to develop the gluten structure of the dough. To do so you want to stretch and fold the dough every half hour for two hours (i.e. 4 times) remembering to recover the dough between each set.
Once you’re done stretching the dough you should cover it again and then leave it on the counter for another two hours.
Time to shape the dough. Flip the dough onto a lightly floured counter and leave it uncovered for 10 minutes. Meanwhile prep your proofing basket. If you don’t have a basket place a kitchen towel in a bowl or a loaf pan and flour the cloth.
Returning to the dough, flip over the dough and then shape it into a round or a batard. To make a round loaf, simply stretch all of the sides into the center, flip it back over and use your hands to rotate the dough on the counter till you have a nice round loaf. For the batard, you want to stretch each of the four sides and fold them into the middle. Then pinch along your seam to create an oval loaf. There are pictures of this process in this post and better pictures of it in my small batch sourdough loaf.
Place the dough, messy side up, in the proofing basket. Cover it and leave it on the counter for half an hour and then refrigerate overnight.
Day 2:
The next day pre-heat the oven to 475°F with the dutch oven in the oven for at least half an hour.
Flip the dough onto parchment paper and then score the loaf.
Loaf the dough into the dutch oven, cover it, and bake for 20 minutes.
Uncover the dough, lower the temperature to 450°F and bake for another 15 minutes.
Allow the bread to cool for at least an hour and then enjoy!