Mix the Levain: In a small bowl or jar, combine the active sourdough starter, flour, and water. Cover and let the levain rise at approximately 78ºF for 3–4 hours.

Fermentolyse: Once the levain has peaked and is active, bubbly, doubled in size, and has a mildly sweet aroma, add 200 grams of levain and 225 grams of water to a large bowl. Reserve the remaining 25 grams of water to add with the salt. Add 360 grams of bread flour and 40 grams of whole wheat flour. Mix until all the flour is incorporated and a shaggy dough forms. Cover and let rest for 30 minutes.

Add the Salt: After 30 minutes, sprinkle the salt over the dough and add the reserved 25 grams of water. Use wet hands to pinch and fold the dough until the salt and water are fully incorporated. Cover and let the dough rest for 30 minutes.

Stretch and Fold: With a wet hand, reach underneath one side of the dough and gently stretch it upward before folding it over the center. Turn the bowl a quarter turn and repeat. Continue until you have stretched and folded all four sides of the dough. Cover and rest for 30 minutes. Complete two more sets of stretch and folds, resting the dough for 30 minutes between each set.

Finish Bulk Fermentation: After the final set of stretch and folds, cover the dough and let it continue rising at about 78ºF. Total bulk fermentation should take approximately 3½ hours from the time the dough was first mixed.

Preshape: Turn the dough out onto the counter. Wet your hands and bench scraper lightly with water, then use the bench scraper to gently pull the dough into a round. Leave it uncovered for 30 minutes.

Prepare the Bowl: Prepare one banneton or small bowl and line it with a hair net or kitchen towel.

Shape the Dough: After the dough has rested for about 30 minutes, shape it into a round. Gather the dough into a tight round or oval, then use a bench knife to transfer it to the prepared banneton or bowl with the seam facing up. Cover it lightly and place in a warm 78-80ºF to rise.

Final Rise: Let the shaped dough rise at approximately 78ºF for about 2 hours.

Preheat the Oven: About 30 minutes before baking, place a Dutch oven inside the oven and preheat to 500ºF.

Score the Dough: Turn the risen dough onto a sheet of parchment paper. Use a bread lame or sharp knife to score across the top of the loaf.

Bake: Carefully lower the dough into the preheated Dutch oven. Reduce the temperature to 450ºF. Cover and bake at 450ºF for 25 minutes. Remove the lid and bake for another 15–20 minutes, or until the crust is deeply golden and the center registers 205–210ºF.