Step 1

For The Levain: Stir flour, water, and starter in 1-cup container until smooth. Cover and ferment as close to 78-80°F (26-27°C) as possible until roughly tripled in volume, about 5 hours (you can use a rubber band to help mark the starting volume).

Step 2

For The Dough: When the levain has 1 hour of fermentation time left, whisk all-purpose flour and whole wheat flour in large bowl until combined, about 30 seconds. Using a wooden spoon or rubber spatula, stir in water until dough forms and no dry spots remain. Cover with plastic wrap and let rest 1 hour at room temperature.

Step 3

Set bowl of dough on digital scale and tare scale to zero. Using a clean wet hand or small rubber spatula, scrape 65g (about 2 1/3 ounces) levain onto dough. (Use leftover levain to continue feeding your starter.) Then, using wet fingers of one hand, dimple levain into dough surface, making sure to evenly distribute it and drive it down into the dough. Massage dough using your fingers and thumb to efficiently incorporate levain. With cupped hand, use a scooping motion to mix dough until starter is well incorporated, about 2 minutes. Cover with plastic wrap and rest for 30 minutes as close to 75°F (24°C) as possible.

Step 4

Sprinkle salt evenly all over dough. Using clean wet fingers, dimple salt thoroughly into dough. With cupped hand, use a scooping motion to mix dough until salt is well incorporated and dough becomes smooth, 2 to 3 minutes. Transfer dough to 8-inch square baking dish. Cover with plastic and rest until dough is loose enough to begin the coil foldings, about 45 minutes at 75°F (24°C). If dough is still too taut, give it more time to relax.

Step 5

First Folding: Using two clean wet hands, slide hands under left and right sides of dough, then lift dough slowly while bringing it towards you slightly; the dough will stretch over your hands while maintaining contact with the top and bottom sides of the vessel. Continue lifting the dough until the dough releases from the top side of baking dish. (If dough stretches and stretches and doesn't lift from top side of baking dish, gently lay the dough you're holding back down, then repeat this lifting and stretching step once more; the top side of dough should release on the second try.) Once top side of dough detaches from baking dish, lay the dough you're holding down onto the top side of the baking dish; the dangling dough will naturally fold under itself when you do this. Rotate vessel 180 degrees. Repeat folding process once more. Rotate dish 90 degrees and repeat folding process with third edge. Rotate dish 180 degrees and repeat folding once more for fourth edge. At this point your dough should have an even square shape. Cover and proof for 60 minutes at 75°F (24°C).

Step 6

Second Folding: Repeat folding instructions from Step Cover and proof for 90 minutes at 75°F (24°C).

Step 7

Third Folding: Repeat folding instructions from Step Cover and proof at 75°F (24°C) until dough has increased in size by roughly 60 percent, and is slightly domed and puffy, 90 to 180 minutes.

Step 8

Shaping: Dust oval banneton lightly with rice flour (if using banneton without liner, dust heavily). Lightly dust dough and counter with all-purpose flour. Uncover dough and invert onto floured counter. Using floured hands, gently pinch right side of dough, stretch it outward about 4 inches, then gently fold over so that edge meets the middle of the dough. Repeat stretching and folding on left side. Starting from top of dough, use both hands to lightly stretch dough about 2 inches, then roll over toward middle of dough; continue to gently roll dough toward yourself until seam is on underside and dough is an even, roughly 9-inch long oval shape. Using your fingers, pinch ends to seal. Using a bench scraper, gently flip dough so that seam is facing up. Using two floured hands, gently pick up dough so that it is cradled lengthwise in cupped palms, then gently lay it seam side up in prepared banneton. Cover and proof at room temperature for 15 to 20 minutes.

Step 9

Place proofed dough in refrigerator set no higher than 38°F (3°C). Let rest overnight, at least 12 hours and up to 16 hours.

Step 10

Scoring and Baking: Cut 9-inch by 7-inch rectangle of parchment paper; trim corners to produce approximate oval shape. Place top and bottom of combo cooker on a rimmed baking sheet set on rack in middle position in oven, and heat oven to 485°F (250°C) for 45 minutes. Remove dough from refrigerator, uncover, and place prepared parchment rectangle on top of banneton. Place a cutting board over parchment. Using both hands, invert so that bottom of banneton is facing up, leaving shaped dough on the parchment; remove banneton. Remove cooker bottom from oven and place on heatproof surface. Using a spray bottle, mist dough lightly with water. Holding bread lame or sharp knife at 10- to 30-degree angle to loaf, make one long, 1/2-inch deep slash running the length of dough. With one hand, hold cutting board with dough and parchment over the combo cooker, and with your other hand, grab parchment by one end, and carefully slide into pan (both parchment and dough). Cover pan with cooker top and place in oven. Bake bread for 20 minutes.

Step 11

Once bread has baked for 20 minutes, remove lid, and reduce oven temperature to 450°F (230°C). Continue to bake until bread is dark brown, blistered, and exposed side shows gradient of browning, about 15 to 20 minutes longer. Transfer pan to a heatproof surface, carefully remove bread from pan, and transfer to a wire rack. Allow bread to cool for at least 2 hours before slicing and serving.