Dill Rosemary Yogurt Spelt Sourdough Boule

Steps

1. Day 1, about 8 am: feed your starter with its usual feed in equal weights, as you normally do, and leave it at about 75°F (24°C). It peaks, doubled and bubbly, in 4 to 6 hours; weigh out the sourdough starter for this recipe then.
2. Toast two-thirds of the sesame seeds in a dry pan until golden, then cool; keep the remaining third untoasted for the crust.
3. In a large bowl, whisk the water, Greek yogurt and olive oil, then mix in the whole spelt flour and the bread flour until no dry patches remain. Cover and rest 30 minutes.
4. Add the sourdough starter and salt and squeeze them through the dough for 3 minutes until even. This dough is about 60% hydration from the water and starter (about 74% counting the yogurt's water) and 1.8% salt; spelt is extensible, so keep it on the firmer side.
5. Sprinkle the dill, rosemary, ground flaxseed, chia seeds and toasted sesame seeds over the dough and fold them in until evenly spread.
6. Bulk rise covered at about 75°F (24°C) for 4 to 5 hours. In the first 2 hours, do 4 sets of gentle stretch-and-folds with wet hands 30 minutes apart, then leave it alone until it has risen about 50%, looks domed and shows bubbles on the sides.
7. Turn the dough onto a clean, lightly dampened counter, pre-shape into a round and rest 20 minutes. Shape a tight boule, mist the top with water and press it into the untoasted sesame seeds.
8. Place it seam side up in a bowl lined with lightly oiled parchment, cover and cold proof in the fridge for 10 to 14 hours overnight.
9. Day 2: preheat the oven to 400°F (200°C) with a rack in the middle and line a baking sheet with parchment.
10. Turn the boule onto the sheet, score a shallow cross and bake 40 to 45 minutes until golden and the center reads 190°F (88°C).
11. Brush the hot crust all over with the melted butter, then cover loosely with a clean kitchen towel to keep the crust soft.
12. Cool on a rack at least 2 hours before cutting into 12 slices.