Feta Rosemary Pumpkin Seed Sourdough Boule

Steps

1. Day 1, 8 a.m.: feed your sourdough starter with its usual 1:1 feeding, kept separate from this recipe's ingredients, and leave it at about 75°F (24°C). It should double and peak, domed and bubbly, in 4 to 6 hours.
2. Meanwhile, toast the pumpkin seeds in a dry skillet over medium heat for 3 to 4 minutes until they pop and smell nutty, then cool. Crumble the feta and keep it in the fridge.
3. About 1 hour before the starter peaks, stir the all-purpose flour and the whole wheat flour with 320 g of the water (all but 20 g) until no dry patches remain. Cover and rest 45 minutes.
4. Add the sourdough starter to the dough and squeeze it through with wet hands for 2 minutes. Sprinkle the salt over the dough, add the remaining 20 g of water, and squeeze and fold until it's absorbed. The dough is about 72% hydration and 1.6% salt (counting the starter's share); the salt is kept low because the feta brings plenty.
5. Bulk rise at about 75°F (24°C) for 4 to 5 hours, covered. After the first 30 minutes, spread the dough out, scatter the feta, rosemary, toasted pumpkin seeds and flaxseed over it, and fold it up to enclose them.
6. Do 3 more sets of stretch-and-folds, 30 minutes apart: lift each side of the dough and fold it over the middle. Then leave it alone until it has risen about 50 to 75%, looks domed and jiggly, and shows bubbles at the sides.
7. Turn the dough onto a clean, lightly dampened counter, pre-shape it into a loose round with wet hands, and rest 20 minutes uncovered.
8. Shape a tight boule by folding the edges into the center and rolling it over to tighten the surface. Mist or wet the top, then roll it in the sesame seeds spread on a plate.
9. Place the boule seam side up in a bowl lined with a sheet of parchment, cover, and cold proof in the fridge overnight, 12 to 16 hours.
10. Day 2: put a Dutch oven with its lid in the oven and preheat to 500°F (260°C) for 45 minutes.
11. Turn the cold dough onto parchment, score the top with a razor, and lower it into the hot Dutch oven. Cover and bake 20 minutes.
12. Remove the lid, lower the heat to 450°F (230°C) and bake 22 to 25 minutes more, until deep brown and crisp and the center reads 205°F (96°C).
13. Cool the bread on a rack for at least 2 hours before cutting into 12 slices, so the crumb sets and the crust stays crisp.