Olive Oil Herb Walnut Sourdough Boule

Steps

1. Day 1, morning: feed your sourdough starter from your own supply in your usual 1:1:1 ratio and leave it at about 75°F (24°C) for 4 to 6 hours, until doubled, domed and bubbly; that is its peak.
2. While the starter rises, toast the walnuts in a dry skillet over medium heat for 5 to 6 minutes until fragrant, cool them, chop roughly, and toss them with the thyme and oregano in a small bowl.
3. About 1 hour before the starter peaks, mix the bread flour and whole wheat flour with all but 30 g of the water until no dry bits remain; cover and rest 1 hour.
4. Add the peaked sourdough starter to the dough and squeeze it in with wet hands for 2 minutes. This dough rises on the starter alone, with no commercial yeast.
5. Sprinkle the salt over the dough with the reserved 30 g of water and squeeze until absorbed; the dough is about 72% hydration and 2% salt.
6. Pour in three quarters of the olive oil (30 g) and squeeze and fold until the dough absorbs it and turns glossy, about 3 minutes.
7. Bulk rise at about 75°F (24°C) for 4 to 5 hours. After the first 30 minutes, spread the dough out, scatter the herbed walnuts over it, and fold it over itself to enclose them; then do 3 more sets of stretch-and-folds every 30 minutes and leave the dough undisturbed for the rest of the bulk.
8. Bulk is done when the dough has grown about 50%, feels airy and shows bubbles on the sides and top.
9. Turn the dough onto a clean, dry counter, pre-shape into a loose round, rest 20 minutes, then shape into a tight boule and place it seam side up in a towel-lined bowl.
10. Cover and cold proof in the fridge for 12 to 16 hours overnight.
11. Day 2: place a Dutch oven with its lid in the oven and preheat to 475°F (245°C) for 45 minutes to 1 hour.
12. Turn the cold boule onto parchment, score a deep cross, brush the top with the remaining quarter of the olive oil (10 g), and press a few shallow fingertip dimples between the cuts, focaccia style.
13. Lower the boule into the hot Dutch oven, cover and bake 20 minutes.
14. Remove the lid, reduce to 450°F (230°C) and bake 25 to 30 minutes more, until the crust is deeply browned and the center reads 205–210°F (96–99°C).
15. Cool the boule on a rack for at least 2 hours before slicing into 12 slices.