Toasted Walnut Pumpkin Seed Sourdough Boule

Steps

1. Feed your sourdough starter the night before, 6 to 8 hours ahead, and leave it at about 75°F (24°C) until bubbly, domed and roughly doubled at its peak.
2. Toast the walnuts in a dry skillet over medium heat for 4 to 5 minutes until fragrant, then cool and chop them roughly.
3. In a small bowl, mix half of the pumpkin seeds and half of the sesame seeds with the flaxseed and 20 g of the water to soak. Set the remaining half of the pumpkin seeds and sesame seeds aside for the crust.
4. In a large bowl, mix the all-purpose flour, the whole wheat flour and 300 g of the water until no dry patches remain. Cover and rest 45 minutes.
5. Add the sourdough starter to the dough and squeeze it in by hand until fully combined. Sprinkle on the salt with the remaining 20 g of water and squeeze again until absorbed. Counting the starter, the dough is about 71% hydration and 2% salt.
6. Begin the bulk rise at about 75°F (24°C). After 30 minutes, add the toasted walnuts and the soaked seed mixture and do the first set of stretch-and-folds to work them in. Do three more sets of stretch-and-folds, 30 minutes apart.
7. Let the dough finish bulk rising undisturbed, 4 to 6 hours in total from adding the starter, until it has grown about 50%, looks domed and bubbly at the edges and jiggles when the bowl is shaken.
8. Turn the dough onto a lightly dampened counter, preshape it into a loose round and rest 20 minutes. Shape it into a tight boule.
9. Mist the top of the boule with water and roll it in the reserved pumpkin seeds and sesame seeds, then place it seam side up in a towel-lined bowl or banneton.
10. Cover and cold proof in the fridge for 12 to 16 hours, until the dough springs back slowly when poked.
11. Place a Dutch oven with its lid in the oven and preheat to 500°F (260°C) for 45 minutes.
12. Turn the cold dough onto parchment, score it with a single deep slash, and lower it into the hot Dutch oven. Cover, reduce the heat to 460°F (238°C) and bake 20 minutes.
13. Uncover and bake 22 to 25 minutes more, until the crust is deep brown and crisp and the center reads 205 to 210°F (96 to 99°C).
14. Cool the bread on a rack for at least 2 hours before slicing into 12 slices.