Step 1

(8:00 a.m.)In a small container, mix the levain ingredients and keep at 74-76°F (23-24°C) for 5 to 6 hours.

Step 2

(12:00 p.m)In a medium mixing bowl, mix the flour and 603 grams water (50 grams is reserved until the next step). Cover and let rest for 1 hour.

Step 3

(1:00 p.m.)To the mixing bowl holding your dough, add the salt, ripe levain (from step 1), and reserved 50 grams water. Mix by hand until incorporated. Transfer your dough to a bulk fermentation container and cover.

Step 4

(1:10 p.m. to 5:10 p.m.)Give the dough 3 sets of stretch and folds at 30-minute intervals, where the first set starts 30 minutes after the start of bulk fermentation.

Step 5

(5:10 p.m.)Lightly flour your work surface and scrape out your dough. Using your bench knife, divide the dough in half. Lightly shape each half into a round shape. Let the dough rest for 25 minutes, uncovered.

Step 6

(5:35 p.m.)Shape the dough into a round (boule) or oval (batard)—place in proofing baskets.

Step 7

(5:40 p.m. to 9:30 a.m. the next day)Cover proofing baskets with reusable plastic and seal shut. Let the dough sit out on the counter for 20 minutes. Then, place both baskets into the refrigerator and proof overnight.

Step 8

(Preheat oven at 8:30 a.m., bake at 9:30 a.m.)Preheat your oven with a combo cooker or Dutch oven inside to 450°F (230°C). When the oven is preheated, remove your dough from the fridge, score it, and transfer to the preheated combo cooker. Place the cooker in the oven, cover with the lid, and bake for 20 minutes. After this time, remove the lid (you can keep it in the oven or remove it) and continue to bake for 30 minutes longer. When done, the internal temperature should be around 208°F (97°C). Let the loaves cool for 1 to 2 hours on a wire rack before slicing.