Maple Milk Oat-Crusted Seeded Sourdough Boule

Steps

1. Day 1, about 8 a.m.: Feed your sourdough starter equal weights of flour and water from your own supply and leave it at about 75°F (24°C). It should peak, doubled, domed and bubbly, in 4 to 6 hours; use it at that peak.
2. Make the oat soaker right after feeding: stir 80 g of the oats (four-fifths of the total) with the milk and the chia seeds in a covered bowl and refrigerate until mixing, so the oats soften and the chia seeds swell into a creamy paste.
3. About 1 hour before the starter peaks, mix the flour and the water in a large bowl until no dry flour remains. Cover and rest 1 hour (autolyse).
4. When the starter peaks, add the sourdough starter, the salt and the maple syrup to the dough. Squeeze and fold with wet hands for 3 to 4 minutes until smooth.
5. Add the oat, milk and chia soaker, the pumpkin seeds and 15 g of the sesame seeds (three-fifths of the total). Pinch and fold until evenly spread; the dough will feel slack at first and tighten as you work it. The water gives about 70% hydration and 2% salt, counting the starter's flour and water; the milk adds more moisture that the oats and chia absorb.
6. Bulk rise, covered, at about 75°F (24°C) for 5 to 6 hours. During the first 2 hours, do 4 sets of stretch-and-folds 30 minutes apart, then leave it alone. Bulk is done when the dough has grown about 50 to 75%, feels airy and jiggles, with bubbles on the sides.
7. Mix the remaining 20 g of the oats with the remaining 10 g of the sesame seeds on a plate for the crust.
8. Turn the dough out onto a lightly floured counter, pre-shape into a loose round and rest 20 minutes. Shape into a tight boule, mist or brush the top with water and press it into the oat and sesame mix to coat.
9. Set the boule seam side up in a floured banneton or towel-lined bowl, cover and refrigerate 12 to 14 hours for an overnight cold proof.
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 boule onto parchment, score one deep slash, and lower it into the hot Dutch oven. Cover, reduce to 475°F (245°C) and bake 20 minutes.
12. Uncover, reduce to 450°F (230°C) and bake 25 to 30 minutes more, until the crust is deeply browned and the center reads 205°F (96°C).
13. Cool the loaf on a rack for at least 2 hours before slicing into 12 slices.