Soft Dill and Onion Seeded Sourdough Batard

Steps

1. The morning before baking (about 8 a.m.), feed your sourdough starter with equal weights of fresh all-purpose flour and water (separate from the recipe amounts) and leave it at about 75°F (24°C); it should peak, doubled and bubbly, in 4 to 6 hours.
2. About an hour before the starter peaks, make the seed soaker: stir the ground flaxseed and the chia seeds into 50 g of the water (part of the total) and let it gel for 30 minutes.
3. Meanwhile, toast the pumpkin seeds in a dry pan over medium heat for 3 to 4 minutes until they pop, then let them cool.
4. In a large bowl, whisk the remaining 120 g of water, the 2% milk, the honey and the peaked sourdough starter until milky. Add the all-purpose flour and the whole wheat flour and mix until no dry patches remain. Cover and rest 30 minutes.
5. Add the salt, the onion powder, the chopped dill and 20 g of the softened butter (two-thirds of the total). Squeeze and fold the dough for 3 to 4 minutes until the butter disappears and the dough feels smooth. This dough is about 65% hydration and 1.8% salt, counting the starter's and the milk's water.
6. Add the flax and chia soaker, the toasted pumpkin seeds and half of the sesame seeds, and fold until evenly spread.
7. 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. Bulk is done when the dough has risen about 50%, looks domed and jiggles with bubbles at the edges.
8. Turn the dough onto a lightly dusted counter, pat it into a rectangle and roll it up tightly into a batard about 10 inches long, pinching the seam closed.
9. Brush the top lightly with water and press it into the remaining half of the sesame seeds. Set it seam side up in a towel-lined oval basket, cover and refrigerate overnight, 10 to 14 hours.
10. In the morning, set the batard on a parchment-lined baking sheet and let it finish proofing at about 75°F (24°C) for 1 to 1½ hours, until puffy and it springs back slowly when poked.
11. Preheat the oven to 375°F (190°C) for 20 minutes. Score the batard once along its length.
12. Bake 35 to 40 minutes, until deep golden and the center reads 190°F (88°C), since this dough is enriched with milk and butter.
13. Right away, brush the hot crust with the remaining 10 g of butter (the last third), then cover the loaf loosely with a clean towel to keep the crust soft.
14. Cool on a rack for at least 2 hours before cutting into 12 slices.