Jalapeño Cheddar Spelt Country Boule

Steps

1. Feed the starter about 8 am in your usual way at 100% hydration and leave it at about 75°F (24°C); it should double and peak, domed and bubbly, in 4 to 5 hours.
2. While the starter rises, cut the cheddar into cubes, seed and dice the jalapeño, and chill both until needed.
3. When the starter peaks, whisk the water, buttermilk and honey in a large bowl, then stir in the starter until milky.
4. Add the whole spelt flour and the bread flour and mix until no dry patches remain. Cover and rest 30 minutes.
5. Sprinkle the salt over the dough and squeeze and fold it in with wet hands for 2 to 3 minutes. The dough is about 71% hydration and 2% salt, counting the starter and buttermilk.
6. After 30 minutes, do the first stretch-and-fold: stretch the dough thin on a damp counter, scatter the cheddar and jalapeño over it, fold it up into a bundle and return it to the bowl.
7. Do 2 more sets of gentle stretch-and-folds 30 minutes apart; spelt dough tears easily, so keep them light.
8. Let the dough finish its bulk rise at about 75°F (24°C), 3 1/2 to 4 1/2 hours from mixing in total, until it has grown by about half, looks airy and jiggles when the bowl is shaken.
9. Turn the dough out, pre-shape into a loose round and rest 20 minutes, then shape a tight boule.
10. Dust a towel-lined bowl with half the cornmeal, set the boule seam side up in it, cover and cold-proof in the fridge 12 to 14 hours overnight.
11. Preheat the oven to 400°F (200°C) with a rack in the middle, and line a sheet pan with parchment dusted with the remaining half of the cornmeal.
12. Turn the cold boule onto the sheet pan, score a shallow cross and bake uncovered 40 to 45 minutes, until golden and 200°F (93°C) in the center.
13. Brush the hot loaf all over with the melted butter, then drape it loosely with a clean towel to soften the crust.
14. Cool on a rack at least 2 hours before cutting into 12 slices.