Honeyed Oat Porridge Seeded Whole Wheat Boule

Steps

1. Evening before, about 9 pm: feed your sourdough starter and leave it at about 75°F (24°C); it should rise, turn bubbly and peak in about 4 to 6 hours, or by morning with a cooler, slower feed. You will need the sourdough starter at its peak for the dough.
2. Divide the oats: set aside 80 g for the porridge soaker and 20 g for the crust. For the soaker, stir the 80 g of oats with the hot milk and the honey in a bowl, cover and let cool to room temperature, at least 1 hour.
3. Morning, when the starter is near its peak: in a large bowl mix the whole wheat flour and the bread flour with 340 g of the water (all but 20 g) until no dry patches remain. Cover and rest 1 hour (autolyse).
4. Add the sourdough starter to the dough and squeeze and fold it in until fully combined. Sprinkle the salt over the dough with the remaining 20 g of water and pinch it in until absorbed. This gives about 75% hydration and 2% salt, counting the starter.
5. Bulk rise at about 75°F (24°C) for 4 to 5 hours. After 30 minutes, spread the oat soaker, pumpkin seeds, ground flaxseed and chia seeds over the dough and fold them in with the first set of stretch-and-folds. Do 3 more sets of stretch-and-folds every 30 minutes, then leave the dough untouched until it has grown about 50%, looks domed and airy and jiggles when the bowl is shaken.
6. Turn the dough onto a clean counter, pre-shape into a loose round and rest 20 minutes. Shape a tight boule with damp hands, then press the top into the reserved 20 g of oats and set it seam side up in a parchment-lined bowl or banneton.
7. Cover and cold proof in the fridge overnight, 12 to 16 hours, until it springs back slowly when poked.
8. Next day, place a Dutch oven with its lid in the oven and preheat to 475°F (245°C) for 45 minutes.
9. Turn the cold dough onto parchment, oat side up, score it with one deep slash, and lower it into the hot Dutch oven. Cover and bake 20 minutes.
10. Remove the lid, reduce the oven to 450°F (230°C) and bake 25 to 30 minutes more, until the crust is deep mahogany brown and the center reads 205°F (96°C).
11. Cool the boule on a rack for at least 2 hours before slicing into 12 slices.