Rosemary Garlic Cheddar Focaccia-Style Sourdough Boule

Steps

1. Day 1, about 8 a.m.: feed your sourdough starter with equal weights of flour and water from your own supply and leave it at about 75°F (24°C) for 4 to 6 hours, until doubled, domed and bubbly. This peaked sourdough-starter is the only leavening.
2. While the starter rises, warm half of the olive oil in a small pan over low heat, add the garlic and cook 1 to 2 minutes until fragrant and pale gold, not brown. Stir in the rosemary and black pepper, then let the garlic oil cool completely.
3. When the starter peaks (about 1 p.m.), mix the flour with all but 20 g of the water until no dry flour remains. Cover and rest 45 minutes.
4. Add the sourdough starter to the dough and pinch and fold until combined. Sprinkle on the salt with the reserved 20 g of water and squeeze it in until smooth. This dough is about 71% hydration and 1.8% salt, counting the starter's flour and water.
5. Spread the cooled garlic-rosemary oil over the dough and fold it in until mostly absorbed.
6. Bulk rise at about 75°F (24°C) for 4 to 5 hours. During the first 2 hours, do 4 sets of stretch-and-folds 30 minutes apart; on the second set, scatter the cheddar over the stretched dough and fold it in. Then leave the dough untouched until it has grown about 50 to 75%, looks domed and jiggly, and shows bubbles on the sides.
7. Turn the dough onto a lightly floured counter, preshape into a loose round and rest 20 minutes. Shape into a tight boule, tucking any cheddar on the surface underneath, and place seam-side up in a floured banneton or towel-lined bowl.
8. Cover and cold proof in the fridge for 12 to 16 hours overnight.
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, brush the top with the remaining half of the olive oil, press a few shallow focaccia-style dimples around the edge and score a deep slash across the center.
11. Lower the dough on the parchment into the hot Dutch oven, cover and bake 20 minutes. Uncover, reduce to 450°F (230°C) and bake 25 to 30 minutes more, until the crust is deep mahogany and the center reads 205°F (96°C).
12. Cool the boule on a rack for at least 2 hours before cutting into 12 slices.