Garlic Parmesan Rosemary Focaccia-Style Sourdough Boule

Steps

1. Day 1, about 8 a.m.: feed your sourdough starter on its usual schedule, keeping it at about 75°F (24°C). It should peak, doubled and bubbly with a domed top, in 4 to 6 hours. The feeding is separate from this recipe's ingredients.
2. While the starter rises, prepare the add-ins: mince the garlic, crumble the rosemary, and set aside 10 g of the Parmesan for the top, keeping the remaining 40 g for the dough. Set aside 25 g of the water for later, and set aside 10 g of the bread flour for dusting.
3. When the starter peaks, stir the sourdough starter into the remaining 350 g of water in a large bowl. Add the remaining 440 g of bread flour and all of the whole wheat flour and mix until nothing dry remains. Cover and rest 45 minutes.
4. Sprinkle the salt and the reserved 25 g of water over the dough and squeeze and fold until absorbed. Then add 20 g of the olive oil and work it in until the dough is glossy and cohesive. The dough is about 75% hydration and 2% salt.
5. Begin the bulk rise at about 75°F (24°C). After 30 minutes, do the first set of stretch-and-folds: lift one side of the dough, stretch it up and fold it over, turning the bowl four times. During this set, scatter in the rosemary, garlic and the 40 g of Parmesan and fold until evenly spread.
6. Do three more sets of stretch-and-folds, 30 minutes apart. Then leave the dough covered until it has grown about 50 to 75%, feels airy and shows bubbles on the sides, 4 to 5 hours from the start of the bulk rise in all.
7. Dust the counter with half of the reserved 10 g of bread flour. Turn the dough out, pre-shape it into a loose round and rest 20 minutes. Dust a basket or towel-lined bowl with the remaining half of the reserved bread flour, shape the dough into a tight boule and set it in seam side up.
8. Cover and refrigerate overnight, 12 to 16 hours, for a cold proof. It is ready when it has puffed and springs back slowly when poked.
9. Day 2: place a Dutch oven with its lid in the oven and preheat to 500°F (260°C) for 45 minutes.
10. Turn the cold boule onto a piece of parchment. Brush the top with the remaining 10 g of olive oil, score it with a sharp blade, and sprinkle the reserved 10 g of Parmesan over the top.
11. Lower the boule into the hot Dutch oven on the parchment, cover, and bake 20 minutes. Reduce the oven to 450°F (230°C), remove the lid and bake 25 to 30 minutes more, until the crust is deeply browned and the center reads 205°F (96°C).
12. Cool the loaf on a rack for at least 1 hour before cutting into 12 slices.