Soft Rosemary Parmesan Seeded Sourdough Batard

Steps

1. Day 1, about 8 a.m.: feed your sourdough starter with equal weights of bread flour and water from your starter supply and leave it at about 75°F (24°C) for 4 to 6 hours, until doubled, domed and bubbly.
2. About 30 minutes before the starter peaks, make a seed soaker: stir the sesame seeds, flaxseed and chia seeds with 60 g of the water (about a quarter of it) in a small bowl and let it gel.
3. Set aside about 15 g of the bread flour for dusting. In a large bowl, whisk the remaining 190 g of water with the milk and the sourdough starter until milky. Add the rest of the bread flour and all of the whole wheat flour and mix until no dry patches remain. Cover and rest 30 minutes.
4. Add the salt, 20 g of the olive oil (four-fifths of it), the Parmesan, the rosemary and the seed soaker with its chia seeds. Squeeze and fold the dough for 3 to 4 minutes until everything is evenly worked in and the dough feels cohesive.
5. Bulk rise covered 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, then leave the dough alone. It is ready when it has grown about 50 to 75%, feels airy and shows bubbles on the sides.
6. Dust the counter with half of the reserved bread flour, turn the dough out, pre-shape into a loose round and rest 20 minutes. Dust a towel-lined bowl or banneton with the remaining reserved bread flour, shape the dough into a snug batard and set it in seam-side up.
7. Cover and cold proof in the fridge overnight, 12 to 14 hours, for flavor and easier scoring.
8. Day 2: Take the dough out about 1 hour before baking; it should spring back slowly when poked. Meanwhile preheat the oven to 400°F (200°C) with a rack in the middle; this moderate heat and no steam keeps the crust soft.
9. Turn the batard onto a parchment-lined baking sheet, score once lengthwise and bake 38 to 45 minutes, until deep golden and 190°F (88°C) in the center, since the milk, oil and cheese enrich the dough.
10. As soon as it comes out, brush the top with the remaining 5 g of olive oil and drape a clean towel over the loaf to soften the crust.
11. Cool the bread completely on a rack, about 2 hours, before cutting it into 12 slices. The formula is about 70% hydration and 1.8% salt, counting the starter's contents and the milk's water.