Toasted Oat Porridge Spelt Sourdough Boule

Steps

1. The night before (about 9 pm), feed your sourdough starter at its usual 1:1:1 ratio; leave it at about 75°F (24°C) for 8–12 hours until bubbly, doubled and peaked.
2. In the morning, toast 80 g of the oats in a dry pot over medium heat for 4–5 minutes until golden and fragrant. Add 160 g of the water and simmer, stirring, 3–4 minutes into a thick porridge. Cool completely, about 30 minutes.
3. Meanwhile, in a large bowl, mix the spelt flour and 100 g of the bread flour with the remaining 320 g of water until nothing dry remains. Cover and rest 45 minutes (autolyse).
4. Add the 100 g of sourdough starter and the salt to the dough and squeeze and fold until fully combined, about 3 minutes. Counting the starter, the dough is about 67% hydration and 2% salt, before the porridge.
5. After 30 minutes, spread the cooled oat porridge over the dough and pinch and fold it in until evenly distributed.
6. Bulk rise at about 75°F (24°C) for 4–5 hours. Spelt is delicate, so do 3 gentle sets of stretch-and-folds 30 minutes apart in the first 1½ hours, then leave it alone. It's ready when it has risen about 50%, looks domed and shows bubbles on the sides.
7. Dust the counter with half of the 15 g of reserved bread flour, turn the dough out, pre-shape into a round and rest 20 minutes uncovered.
8. Dust a proofing basket or towel-lined bowl with the remaining half of the reserved bread flour. Shape the dough into a tight boule, mist or brush the top lightly with water and roll it in the remaining 20 g of oats. Place it seam-side up in the basket.
9. Cover and cold proof in the fridge for 10–14 hours overnight.
10. The next morning, place a Dutch oven with its lid in the oven and preheat to 475°F (245°C) for 45 minutes.
11. Turn the cold dough onto parchment, score the top with a sharp blade, 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 22–25 minutes more until the crust is deeply browned and the center reads 205–210°F (96–99°C).
13. Cool the loaf on a rack for at least 2 hours before slicing into 12 slices; the porridge crumb needs time to set.