In a warm kitchen, making this bread from start to finish can take as little as 8 hours. In a cooler kitchen and with a refrigerated final proof, this bread can take much longer. My dough rose at cool room temps for 7 hours, and then was in the refrigerator for a 12-hour final proof.

Combine the 60 grams black sesame seeds, sugar, and water in a spice grinder. You can also use a food processor, but you may need to make extra paste, e.g. double the ingredients, to reach the blades.

Place the dough ingredients in a bowl and mix. I used a stand mixer, but hand mixing is also fine. The dough will be relatively loose and wet but should be strong enough to coil fold in about 90 minutes.

Divide the dough into two slightly unequal parts, for example 540 grams and 460 grams. This doesn't have to be precise. Place each dough in a bowl or bucket and cover.

About 30 minutes after the initial mixing, do a round of stretching and folding on each dough.

About 60 minutes after mixing, stretch and fold the larger dough. Add the sesame paste to the smaller dough and mix thoroughly. Both doughs will be about the same size now.

About 90 minutes after mixing, coil fold both doughs.

About 2 hours after mixing, lightly dampen a large work space with water and stretch both doughs into rectangles. Using a bench knife, lift the gray dough and lay it on the white dough. (The reverse is fine too.) The rectangles don't have to be perfectly aligned. Fold the layered dough in thirds like a letter, then fold it in thirds again on the short edge. Return the combined dough to one of the buckets/bowls, press it down, and mark the level of the dough as best as you can.

Do a final round of coil folding about 30 minutes after the lamination unless you want larger, more distinct color sections.

When the dough has expanded by 30-50% relative to the level set after the lamination, the bulk fermentation is complete. This may take several more hours.

Prep a plate or tray with sesame seeds for the crust.

Transfer the dough to a lightly floured work surface and shape it to your preference: boule, batard, oblong loaf.

While the dough is resting on its seam, brush the top and sides with water. Scoop up the dough with a bench knife and flip it onto the seeds. Grasping the bottom seam of the dough, roll it around the seeds to coat all but the bottom of the dough.

Place the dough seam-side up in a proofing basket. If any damp portions of the dough touch the basket, gently pull the dough away from the basket and sprinkle in some extra seeds for a non-stick barrier.

For a same-day bake, let the dough proof at room temperature 1-3 hours or until it has expanded and is puffy. To deepen the sourdough flavors, refrigerate the dough for 8-16 hours. If the ambient temperature is already cool (under 70°F), leave the dough at room temperature for about 40 minutes before refrigerating it. You don't need to let the dough warm up before baking.

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

Flip the dough out of the proofing basket and onto a sheet of parchment paper or silicone sling and score.

Bake at 500°F for 15 minutes, lid on (option to re-score the dough at the 7-minute mark)

450°F for 10 minutes, lid on

450°F for 10 minutes, lid off

Let the bread cool for a couple hours before cutting it.