Oat-Crusted Country Sourdough Boule

Steps

1. Day 1, about 8:00 a.m.: feed your sourdough starter from your own supply (not the recipe amounts) with equal weights of fresh bread flour and water, and leave it at about 75°F (24°C). It will peak, doubled, domed and bubbly, in 4 to 6 hours. You need 100 g of the fed starter for this loaf.
2. Make the oat soaker while the starter rises: pour the boiling 80 g portion of the water over the 60 g soaker portion of the oats, stir, cover and let cool to room temperature, about 1 hour. Set the remaining 20 g of oats aside for the crust.
3. About 1 hour before the starter peaks, mix the bread flour and the whole wheat flour with the lukewarm 280 g portion of the water until no dry bits remain. Cover and rest (autolyse) for 1 hour.
4. Add the peaked sourdough starter to the dough and squeeze and fold it in until fully combined, about 3 minutes.
5. Sprinkle the salt over the dough, add the final 30 g portion of the water and pinch it in until the dough comes back together. Then fold in the cooled oat soaker until evenly spread. The dough works out to about 80% hydration and 2% salt, counting the starter and the soaker water; the oats soak up much of it.
6. Bulk rise at about 75°F (24°C) for 4 to 5 hours. During the first 2 hours, do 4 sets of stretch-and-folds 30 minutes apart: with wet hands, lift each side of the dough and fold it over the center. Then leave it covered until it has grown about 50%, looks domed with bubbles on the sides and jiggles when the bowl is shaken.
7. Turn the dough onto a clean, bare counter, pre-shape it into a loose round and rest it uncovered for 20 minutes.
8. Shape a tight boule by folding the edges into the center, flipping it seam-side down and dragging it toward you to build surface tension.
9. Lightly wet the top of the boule with damp hands, then roll the top in the reserved crust oats so they stick. Place it oat-side down in a towel-lined bowl or banneton; the oat coating keeps it from sticking.
10. Cover and cold proof in the fridge overnight, 12 to 16 hours. It is ready when it springs back slowly when poked.
11. Day 2: put a Dutch oven with its lid in the oven and preheat to 500°F (260°C) for 45 minutes.
12. Turn the cold boule onto parchment so the oats face up, and score a deep slash or cross across the top with a sharp blade.
13. Lower the loaf on its parchment into the hot Dutch oven, cover, reduce the oven to 475°F (245°C) 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 loaf on a rack for at least 2 hours before slicing into 12 slices, so the crumb can set.