Toasted Walnut Honey Whole Wheat Sourdough Batard

Steps

1. The night before mixing (about 8 to 12 hours ahead), feed your sourdough starter from your usual starter supplies, separate from this recipe's amounts, and leave it at about 75°F (24°C); it should peak, doubled and bubbly, in about 6 to 8 hours, and you need it fed and bubbly for this loaf.
2. Toast the walnuts in a dry skillet over medium heat, stirring, for 4 to 5 minutes until fragrant, then cool and chop roughly.
3. Make the seed soaker: stir the pumpkin seeds, sesame seeds and flaxseed with about one-tenth of the water (roughly 40 g) in a small bowl and set aside.
4. In a large bowl, mix the whole wheat flour and bread flour with about three-quarters of the water (roughly 285 g) until no dry patches remain. Cover and rest 1 hour at about 75°F (24°C).
5. Add the sourdough starter, the honey and the salt to the dough with the remaining water (roughly 55 g). Squeeze and fold with wet hands for 3 to 5 minutes until smooth. The dough is about 78% hydration and 2% salt, counting what is in the starter.
6. Add the toasted walnuts and the seed soaker and fold them in until evenly spread through the dough.
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, then leave the dough alone until it has grown about 50%, looks domed and airy at the edges, and jiggles when the bowl is shaken.
8. Turn the dough onto a lightly dampened counter, pre-shape into a loose round with wet hands and rest 20 minutes. Shape into a tight batard by folding the sides in and rolling it firmly from the top to build tension, which gives an even crumb for sandwiches.
9. Place it seam side up in a bowl or banneton lined with parchment or a clean, well-dusted towel, cover, and cold proof in the fridge for 12 to 16 hours, until it springs back slowly when poked.
10. Put a Dutch oven with its lid in the oven and preheat to 475°F (245°C) for 45 minutes.
11. Turn the cold loaf onto parchment, score one long slash down its length, and lower it into the hot Dutch oven. Cover and bake 20 minutes.
12. Remove the lid, lower the heat to 450°F (230°C) and bake 25 to 30 minutes more, until the crust is a deep mahogany brown and the center reads 205°F (96°C).
13. Cool the loaf on a rack for at least 2 hours before cutting into 12 slices.