Rosemary Parmesan Rye Country Boule

Steps

1. Day 1, morning: feed your sourdough starter from your own jar with equal weights of fresh rye flour and water (separate from this recipe's amounts) and leave it at about 75°F (24°C). It peaks in 4 to 6 hours, when it has doubled, is domed and full of bubbles.
2. Prepare while the starter rises: weigh out the rye flour and set aside about 10 g of it for dusting, keeping the remaining 290 g for the dough. Cube the cheddar, crumble the rosemary, and divide the Parmesan into two portions, about three quarters (45 g) for the dough and the remaining quarter (15 g) for the crust. Chill the cheddar until needed.
3. When the starter peaks, stir the sourdough starter into the water in a large bowl until milky. Add the dough portion of rye flour and the bread flour and mix until no dry rye or bread flour remains; the dough will be sticky and paste-like, as rye doughs are. This is about 76% hydration and 1.8% salt.
4. Cover and rest 30 minutes, then sprinkle the salt over the dough and squeeze it in with wet hands until evenly mixed.
5. Add the rosemary, black pepper and the dough portion of Parmesan, and fold them through until evenly distributed.
6. Bulk rise at about 75°F (24°C) for 4 to 5 hours. During the first 90 minutes, do 3 sets of stretch-and-folds 30 minutes apart with wet hands, adding the cheddar cubes during the first set and folding them in. Then leave the dough undisturbed until it has grown by about half, looks puffy and shows small bubbles on the surface.
7. Shape: dust a banneton or towel-lined bowl with about half of the reserved dusting rye flour and the counter with the other half. Turn the dough onto the counter, gently fold the edges into the center, flip it seam-side down and use wet hands to tighten it into a round boule. Place it seam-side up in the banneton.
8. Cover and cold proof in the fridge for 12 to 14 hours overnight; the dough should look slightly puffed and spring back slowly when poked.
9. Day 2: place a Dutch oven with its lid in the oven and preheat to 475°F (245°C) for 45 minutes.
10. Turn the cold dough onto parchment, score a deep cross on top, and lower it into the hot Dutch oven. Cover and bake 25 minutes.
11. Remove the lid, scatter the crust portion of Parmesan over the top, reduce the oven to 450°F (230°C) and bake 20 to 25 minutes more, until the crust is deeply browned and the center reads 205 to 210°F (96 to 99°C).
12. Cool the loaf on a rack for at least 3 hours before slicing into 12 slices, so the rye crumb can set and stay moist rather than gummy.