This dough had a 7-hour bulk fermentation (calculated from the initial mixing) at 78°F and a 13-hour refrigerated final proof. With different temperatures or more or less sourdough starter, you can modify this timing.

In the bowl of a stand mixer, whisk together the water, sourdough starter and pinch of crushed vitamin C tablet.

Add the flours and salt, and mix on low speed with the dough hook attachment for 1-2 minutes. The dough will be somewhat shaggy and sticky.

Cover the bowl and let the dough rest for one hour.

Mix again, now on med-high speed, for 12 minutes. The dough will wrap around the hook and look silky by the end of the mixing.

Transfer the dough to a straight-walled container if you have one. Cover and let it rise until it is between 1.5x and 2x the original size, an expansion of 50-100%.

Scrape the dough out onto a lightly floured work surface and shape it to your preference (boule, batard, oblong loaf). Make sure you build tension on the surface of the dough and dust it with flour before placing it seam-side up in your proofing basket.

Cover the basket and refrigerate it for 12+ hours.

Preheat your oven and baking vessel to 500°F for 30 minutes.

Directly from the refrigerator, flip the dough out of the proofing basket and onto a sheet of parchment paper or a silicone bread sling. Score and load into your baking vessel and oven.

Bake for 12 minutes, then reduce the oven temperature to 375°F. Bake for 45 minutes more or until the internal temperature of the bread is over 205°F. Keep the lid on the entire time. (You can remove the lid as needed to use a probe thermometer toward the end of the bake.)

Let the bread cool for several hours before you slice it.