Refresh the starter: 6 to 8 hours before mixing your dough, take your sourdough starter out of the refrigerator and place 15 grams of the starter into a clean, empty jar. Discard any starter left in the original jar. Add the 60 grams of flour and 60 grams of water to the jar and stir well. Leave the refreshed starter out at room temperature for 6 to 8 hours until it doubles in volume and becomes bubbly. (After using what’s needed for the recipe, keep the remainder for your next refresh.)
Scale: Place a mixing bowl on the scale, tare the weight of the scale, and pour in 360 grams of water. Add 100 grams of the active starter and the whole-wheat and all-purpose flour. (When using the scale to measure ingredients, use the tare function to remove the weight of the mixing bowl and other previous ingredients so you can weigh each individual ingredient easily as you add each one to the bowl.)
Mix: Using a spoon, mix the ingredients together (if you have a stand mixer and a dough hook, mix until the dough starts to pull away from the sides of the bowl) and knead for about 5 minutes. There should be no dry spots of flour. After the initial mixing, it can be helpful to mix the dough with your hands or with a plastic dough scraper to make sure that all the water is incorporated into the flour. Be sure to scrape the sides of the bowl so no dry pieces of dough stick to it.
Autolyse: Cover the bowl and rest the dough for at least 20 minutes and up to 60 minutes.
Add salt: Tare the mixture and add the 10 grams of salt and the final 10 grams of water to dissolve the salt. Continue folding the dough, rotating and folding it to make sure it is fully mixed, at least 5 minutes.
Rest: Cover the bowl and let rest at room temperature for 30 minutes.
Stretch and fold: To further strengthen dough, pull up one quarter of the dough and fold it over the middle. Repeat this process with the other three quarters of the dough. Recover the dough. This step can be done up to 4 times for maximum development of dough strength during the bulk fermentation.
Bulk fermentation: Let the dough ferment at room temperature for at least 2 hours, and up to 4 hours, until the dough is 1 ½ times its original size and has a smooth texture.
Preshape and bench rest: Transfer the dough from the bowl onto an unfloured clean work surface. Quickly push the dough scraper under one half of the dough fold the dough over itself. Push the scraper under one side of the dough and rotate it in a circle 3 to 5 times until it forms a rough ball. Leave the dough to rest for 20 minutes.
Prepare the proofing bowl: Dust a proofing bowl or an 8-inch-wide colander lined with a kitchen towel generously with rice flour or cornmeal so that the sides and bottom have a thick, even coating.
Final Shape: Lightly flour the work surface and the top of the preshaped dough round. Using the dough scraper, push under the entire piece of dough and, using your opposite hand to guide the dough, lift it off the work surface, and flip it onto its floured side. The sticky, unfloured side of the dough should be facing up. Take two opposite edges of dough and gently pull them up creating some length without tearing the dough (if the dough tears, stop stretching and continue with the steps). Fold the edges into the middle of the dough, one on top of the other, using the sticky edges to help them adhere to each other. The dough will look a bit like a burrito. Taking the end of the dough below the seam, gently lengthen with a slight stretching motion and roll the dough onto itself in a spiral until it seals at the opposite end. The floured side of the dough should be facing up and from the side the rolled dough should look like a baby’s bottom. The dough has structure but still needs tension. Using a bench scraper, pull the dough across the work surface or rotate it in a circle, without flipping the dough over, until it tightens into a taut ball. Quickly push the scraper under the dough, lift it off the work surface, guiding it with the opposite hand, and flip the dough upside down into the prepared proofing bowl. The floured side should be down.
Proof: Cover the dough and proof for 1 to 2 hours at room temperature, until a finger lightly pressed into the dough slowly rises back.
Preheat: 30 to 60 minutes before the proofing is done, preheat the oven to 500º Place a Dutch oven or cloche inside the oven on the center rack to preheat. If you don’t have a Dutch oven or cloche, place a metal pan of water on the lowest rack to steam during preheat and the first half of the bake.
Bake: Cut a large piece of parchment paper that is approximately twice as wide as the dough. Center the parchment paper over the proofing bowl and flip the bowl upside down to release the dough onto the paper. Using a serrated bread knife or a bread lame, cut a slit all the way across the top of the dough, about ¼-inch deep. Carefully transfer the dough from the parchment paper into the preheated Dutch oven or cloche (or onto a cookie sheet, if using the manual steam method) and cover it with the lid. Place the bread in the oven. Reduce the oven temperature to 460º F and bake for 20 minutes. Carefully remove the bread from the Dutch oven and place it directly onto the oven rack (remove the steam tray if using manual steam). Reduce the heat to 450º F and bake for an additional 20 minutes to create a golden-brown crust.
Cool: Transfer the bread to a cooling rack and allow it to cool for at least 60 minutes before slicing.