Soft Maple Walnut Country Sourdough Boule

Steps

1. The night before (about 10 pm), feed your sourdough starter from your usual supply with equal weights of its regular feed and water, separate from the recipe amounts; leave it at about 75°F (24°C) for 8 to 12 hours until doubled, bubbly and domed at its peak.
2. Meanwhile, toast the walnuts in a dry skillet over medium heat for 5 to 6 minutes until fragrant, cool, and chop.
3. In the morning, whisk the water, milk, almond butter and maple syrup in a large bowl until smooth.
4. Stir in the bread flour and whole wheat flour until no dry bits remain; cover and rest 45 minutes.
5. Add the sourdough starter and salt and squeeze them through the dough until fully mixed, then work in half of the butter until absorbed; set the remaining half of the butter aside for brushing. The dough is about 69% hydration counting the water and milk, and 2% salt.
6. Cover and let 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, scattering the walnuts over the dough before the second set and folding them in.
7. Bulk is done when the dough has grown about 50%, looks domed and airy, and jiggles when the bowl is shaken.
8. Turn the dough onto a clean counter, pre-shape into a round, rest 20 minutes, then shape a tight boule and place it seam side up in a towel-lined banneton or bowl.
9. Cover and cold proof in the fridge for 10 to 14 hours, until it springs back slowly when poked.
10. Preheat the oven to 400°F (200°C) with a rack in the middle and line a baking sheet with parchment.
11. Turn the cold boule onto the parchment, score the top, and bake uncovered for 40 to 45 minutes until deep golden and 190°F (88°C) or more in the center.
12. Melt the remaining half of the butter and brush it over the hot loaf right away, then cover loosely with a clean towel to soften the crust.
13. Cool on a rack for at least 2 hours before cutting into 12 slices.