The night before making your dough, feed your starter a 1:5:5 feeding ratio by mixing 15 g sourdough starter, 75 g water, and 75 g bread flour. This gives you 45 extra grams, so you don’t have to scrape the jar clean (use the leftovers to maintain your starter). At this ratio, your starter should peak in 10-12 hours.Starting in the morning instead? Use a 1:1:1 ratio for a faster peak (4-6 hours). Combine 50 g starter, 50 g water, and 50 g bread flour.
Make the Dough
In the morning, when your starter has peaked (see Recipe Notes for help), mix 325 g water, 120 g of your active sourdough starter, 10 g sea salt, 400 g bread flour, and 100 g whole wheat flour in a bowl. Mix until the ingredients are fully combined and the dough is shaggy. Cover the bowl with plastic wrap, a shower cap, or a cloth, and let it rest for 30 minutes. (This is the beginning of the bulk fermentation.)
Set aside 57g (4 tbsp) of butter on the counter to soften for later.
After 30 minutes, perform your first set of stretch and folds (or coil folds). Repeat this every 30 minutes for a total of 3-5 rounds, until the dough becomes smoother, holds its shape better, and stretches with a little resistance instead of feeling loose. If you’re unsure, aim for 4 rounds to be safe. Once finished, cover the dough and let it rest until bulk fermentation is complete.
Bulk fermentation is done when the dough is visibly larger (the exact percentage rise is not as important as the other visual signs), with bubbles all around the sides and underneath the surface. The dough should jiggle like jello when you shake the bowl and feel light, airy, and puffy to the touch. It should be domed on the edges where the dough meets the bowl. Don’t worry about exact timing; trust these visual and tactile cues to guide you. Warmer dough ferments faster, colder dough takes longer, but slightly overproofed dough often makes better bread than underproofed. Don't be afraid to push the limits. For this recipe, my bulk fermentation took 8 hours at a 70°F (21°C) average temperature. Another test at 75°F (24°C) took just under 6 hours.
When the bulk fermentation is done, lightly mist your work surface with water and dump out the dough. Gently stretch it into a 13" x 16" rectangle with the long side at the bottom.
Add the Filling, Shape, & Cold Retard
In a small bowl, mix 57 g softened butter, 8 g cinnamon, 65 g brown sugar, and 8 g bread flour.
Using a silicone spatula, spread half the cinnamon sugar mixture evenly down the center of the dough, leaving about 4 inches clear along each short side.
Fold the dough’s sides to the center and pinch all the seams closed.
Spread the rest of the cinnamon sugar filling evenly over the top, leaving about an inch on each side for sealing.
Roll the dough tightly into a log, pinching the edges to seal as you roll. When you get to the end, gently pinch the seam to close it up.
Place seam-side up into a floured, towel-lined banneton. Cover and refrigerate overnight (8 hours up to 4 days; overnight is best).
Score & Bake
The next day (or after at least 8 hours in the fridge), preheat your oven to 450°F (230°C) with a Dutch oven or bread dome inside.
Flip the dough onto parchment paper, score the top, and bake for 30 minutes covered and 10–15 minutes uncovered (watch closely to prevent burning).
The bread is done when it reaches an internal temperature of 205–210°F (96–99°C).