Soft Whole Wheat Country Sourdough Boule

Steps

1. The night before (about 8–12 hours before mixing), feed your sourdough starter its usual feed of equal weights of grain and water (separate from this recipe) and leave it at about 75°F (24°C); it peaks, doubled and bubbly, in 4–8 hours. Use it at its peak.
2. Autolyse: in a large bowl, stir the whole-wheat flour and the bread flour with the water until no dry patches remain. Cover and rest 45 minutes so the bran softens.
3. Add the sourdough starter, the milk, the honey and two-thirds of the olive oil to the dough and squeeze them in by hand until even, about 3 minutes.
4. Sprinkle the salt over the dough and squeeze and fold for 2–3 minutes until it is fully worked in. This dough is about 78% hydration (counting the water, the milk's water and the starter's water against the whole-wheat flour, bread flour and the starter's grain) and 2% salt.
5. Bulk rise at about 75°F (24°C) for 4–5 hours: do 4 sets of stretch-and-folds 30 minutes apart during the first 2 hours, then leave the dough covered. It is ready when it has grown about 50%, feels airy and shows bubbles on the sides.
6. Rub the remaining third of the olive oil over a clean counter, turn the dough onto it, pre-shape it into a loose round and rest it 20 minutes uncovered.
7. Shape a tight boule by folding the edges to the center and rolling it over to build surface tension. Set it seam-side down on a sheet of parchment inside a bowl.
8. Cover and cold proof in the fridge for 12–16 hours. It is ready when it springs back slowly when poked.
9. Preheat the oven to 450°F (230°C) with a baking sheet inside for 45 minutes, and put an empty metal pan on the lowest rack.
10. Lift the cold boule out on its parchment, score the top, slide it onto the hot sheet and pour 1 cup of hot tap water (not listed, for steam) into the empty pan. Bake 20 minutes.
11. Lower the oven to 400°F (200°C), remove the steam pan and bake 20–25 minutes more, until deep brown and 205°F (96°C) in the center.
12. Brush the hot crust all over with the melted butter, then cover the loaf loosely with a clean towel as it cools to keep the crust soft.
13. Cool on a rack at least 2 hours before cutting into 12 slices.