Honey Walnut Seeded Sourdough Boule

Steps

1. The night before mixing, feed your sourdough starter on its usual equal-weight schedule and leave it at about 75°F (24°C) until bubbly, doubled and at its peak, usually 4 to 8 hours after feeding.
2. Toast the walnuts in a dry skillet over medium heat for 4 to 5 minutes until fragrant, then cool and chop. Toast the pumpkin seeds and all of the sesame seeds the same way for 2 to 3 minutes, then cool.
3. Stir the flaxseed into 30 g of the water in a small bowl and set aside to soak; this is the seed soaker.
4. In a large bowl, mix the all-purpose flour and the whole-wheat flour with 260 g of the water until nothing dry remains. Cover and rest 45 minutes (autolyse).
5. Add the sourdough starter and the honey to the dough and squeeze them in with wet hands until even, about 3 minutes.
6. Sprinkle the salt over the dough with the remaining 30 g of the water and squeeze and fold until absorbed. Counting the starter, the dough is about 74% hydration and 2% salt.
7. Cover and rest 30 minutes at about 75°F (24°C), then spread the dough out and scatter over it the walnuts, the pumpkin seeds, half of the sesame seeds and the flaxseed soaker; fold and squeeze until evenly distributed.
8. Bulk rise at about 75°F (24°C) for 4 to 5 hours, doing a set of stretch-and-folds every 30 minutes for the first 2 hours (4 sets). Bulk is done when the dough has grown about 50%, looks domed and jiggly, and shows bubbles on the sides.
9. Turn the dough onto a clean counter, pre-shape into a loose round and rest 20 minutes uncovered.
10. Shape into a tight boule, mist the top lightly with water and roll it in the remaining half of the sesame seeds. Place seam side up in a towel-lined banneton or bowl.
11. Cover and cold proof in the fridge overnight, 12 to 16 hours.
12. Place a Dutch oven with its lid in the oven and preheat to 500°F (260°C) for 45 minutes.
13. Turn the cold dough onto parchment, score it with a sharp blade, and lower it into the hot Dutch oven. Cover and bake 20 minutes.
14. Remove the lid, lower the heat to 450°F (230°C) and bake 25 to 30 minutes more until the crust is deeply browned and the center reads 205 to 210°F (96 to 99°C).
15. Cool the bread on a rack for at least 2 hours before slicing into 12 slices.