Toasted Pecan Cheddar Maple Sourdough Batard

Steps

1. Morning of day 1: feed your sourdough starter with equal weights of flour and water and leave it at about 75°F (24°C) for 4 to 6 hours, until doubled, domed and bubbly; you'll use the sourdough starter at this peak.
2. While the starter rises, toast the pecans in a dry skillet over medium-low heat for 5 to 7 minutes, stirring, until fragrant; cool completely, then chop roughly. Cube the cheddar and chill it until needed.
3. About 1 hour before the starter peaks, stir the bread flour, the water, the milk and the maple syrup in a large bowl until no dry flour remains. Cover and rest 45 minutes.
4. Add the peaked sourdough starter and the salt to the dough and squeeze and fold with wet hands for 3 to 4 minutes until fully combined. The dough is about 73% hydration (counting the starter's water and the milk's water) and about 1.8% salt.
5. Divide the butter: use three-quarters of the butter now and keep the remaining quarter for brushing the baked loaf. Work the three-quarters of the butter into the dough in pieces, squeezing and folding until it disappears and the dough turns glossy, about 5 minutes. Cover.
6. Bulk rise at about 75°F (24°C) for 4 1/2 to 5 1/2 hours. After 30 minutes, gently stretch the dough into a thin rectangle on a damp counter, scatter the pecans and the cheddar over it, and fold it up like a letter, then roll it back into a ball.
7. Give 3 more sets of stretch-and-folds every 30 minutes, then leave the dough undisturbed until it has risen about 60 to 75%, looks domed and airy and jiggles when the bowl is shaken.
8. Turn the dough onto a lightly floured counter, pre-shape into a loose round and rest 20 minutes. Shape into a tight batard, tucking any exposed cheese underneath, and place it seam side up in a floured banneton or towel-lined bowl.
9. Cover and cold proof in the fridge for 12 to 14 hours overnight.
10. Day 2: line a baking sheet with parchment and preheat the oven to 400°F (204°C) for 45 minutes, with a rack in the middle. Turn the cold dough onto the parchment, seam side down, and score one long slash down its length.
11. Bake for 40 to 45 minutes, until deep golden and the center reads 190°F (88°C) on an instant-read thermometer; tent loosely with foil after 25 minutes if the cheese browns too quickly. The moderate oven and open baking keep the crust soft.
12. Melt the remaining quarter of the butter and brush it over the hot loaf right away to soften the crust.
13. Cool the loaf on a rack for at least 2 hours before slicing into 12 slices, so the crumb sets.