Sourdough Multigrain Sandwich Bread

Ingredients

The Levain (Day 1, Evening)

• 50g ripe sourdough starter, 100% hydration • 3½ tablespoons
• 100g bread flour • ¾ cup plus 1 tablespoon
• 100g water (about 80F / 27C) • ⅓ cup plus 2 tablespoons

The Soaker (Day 1, Evening)

• 150g seven grain hot cereal, uncooked • ¾ cup plus 2 tablespoons
• 300g boiling water • 1⅓ cups
• 3g fine sea salt • ½ teaspoon

The Dough (Day 2, Morning)

• 500g bread flour • 4 cups plus 3 tablespoons
• 200g white whole wheat flour • 1¾ cups
• 360g whole milk, lukewarm (about 90F / 32C) • 1½ cups
• 80g honey • ¼ cup
• 50g unsalted butter, softened • 3½ tablespoons
• 14g fine sea salt • 2¼ teaspoons

The Top

• 15g whole milk, for brushing • 1 tablespoon
• 15g old-fashioned rolled oats • 3 tablespoons

Method

1. Stir the ripe starter, flour, and water together in a jar until smooth. Mark the level with a rubber band so you can see how far it climbs.
2. Cover loosely and leave it at room temperature, ideally around 72F to 76F (22C to 24C), for 10 to 12 hours. It's ready when it's roughly doubled, domed on top, and webbed with bubbles underneath.
3. Put the cereal and salt in a medium heatproof bowl. Pour the boiling water over it and stir well until there are no dry pockets at the bottom.
4. Cover and leave it on the counter next to the levain. By morning it's a thick, cool porridge that holds its shape on a spoon.
5. Drop a teaspoon of levain into a glass of water. If it floats, you're on. If it sinks, give it another hour or two and check again. Don't push forward with a levain that isn't ready.
6. Put both flours, the milk, honey, salt, the whole levain, and the whole soaker in the mixer bowl. Mix on low for 2 to 3 minutes until there's no dry flour anywhere. It looks rough. Let it look rough.
7. Cover and rest. This autolyse matters more in the sourdough version than the yeasted one, because you've got a long fermentation ahead and softened bran is what keeps the crumb from going crumbly on day two.
8. Add the softened butter in pieces on low speed, then mix on medium-low for 8 to 10 minutes. The dough should clear the bowl sides and feel supple, tacky but not sticky. By hand, use slap-and-fold for 10 minutes with two 5 minute rests worked in.
9. Move the dough to a lightly oiled straight-sided container. Mark the starting level with tape or a rubber band. With this much grain in the dough, that mark is the only honest way to read the rise.
10. At 45, 90, and 135 minutes, give the dough a set of stretch-and-fold. Wet your hand, reach under one side, lift, and fold it over the center. Turn the bowl and repeat four times. Then leave it alone.
11. Total bulk is 4 to 5 hours at 76F to 78F (24C to 26C). You're looking for the dough to grow by about 50%, feel airy and domed, and show bubbles at the edges. Do not chase a doubling here. An enriched sourdough that doubles in bulk has nothing left for the pans.
12. Turn the dough out onto a lightly floured counter and divide it into two equal pieces, about 950g each. Weigh them so both loaves rise to the same height.
13. Round each piece loosely and let them sit uncovered for 15 minutes. This bench-rest relaxes the dough so the final roll doesn't fight you.
14. Pat each piece to a rectangle as long as your pan, then roll it up tightly from the short edge, pinching the seam as you go. Press out any large pockets you feel under your palms.
15. Seam side down in greased 9 by 5 pans, pressed gently into the corners. Cover well so the tops don't dry out overnight.
16. Cover the pans and refrigerate for 12 to 16 hours. The dough rises slowly and finishes somewhere near the rim of the pan. Up to 20 hours is fine if your morning gets away from you, and the flavor only gets better.
17. You want the dough crowning about ½ inch above the rim. If it's still below the rim, leave the pans on the counter for 1 to 2 hours until it gets there. If it's well above the rim, bake right away straight from cold.
18. Preheat to 350F (175C). While it heats, brush the cold loaf tops with milk and scatter the oats over them.
19. Bake on the lower-middle rack for 40 to 45 minutes, rotating front to back at 25 minutes. Tent with foil if the tops go dark before the 30 minute mark.
20. Pull at 200F to 205F (93C to 96C) in the center. Sourdough runs a few degrees higher than the yeasted version because the crumb is denser and holds moisture longer.
21. Out of the pans immediately onto a wire rack. Cool a full 3 hours before slicing. Sourdough multigrain needs longer than a yeasted loaf, and cutting early gives you a gummy crumb that isn't the recipe's fault.