Combine the flour, water, and starter for the sourdough build 12 to 18 hours before you plan to mix the dough. Let sit at room temperature until doubled in volume.

Once the build has doubled, combine all dough ingredients in the bowl of a stand mixer fitted with the hook attachment. If using active dry yeast, add it directly with the other ingredients. There is no need to bloom it first.

Mix on the lowest speed until all ingredients are incorporated and a rough dough forms. If the butter was cold, some may remain unincorporated at this stage, which is fine.

Increase speed to medium (speed 6 on a KitchenAid 5-quart) and mix for about 6 minutes, until the dough passes the windowpane test (when a small piece stretches thin without tearing). Note that this lower-hydration dough will look different from a brioche windowpane.

Turn the dough out onto a clean surface and divide into 12 equal pieces, roughly 100g each. Keep all pieces covered with plastic wrap as you work.

Preshape each piece by stretching it gently into a small rectangle, folding each short side toward the center, then performing two sets of thumb folds as you would when shaping a loaf. Fold the top over your left thumb and seal with your right thumb. Roll gently to seal the seam and lengthen the rope as much as the dough allows. Place under plastic and repeat with all pieces.

Let the preshaped pieces bench rest, covered, for 30 minutes. Do not rush this step.

Line two rimmed baking sheets with parchment paper and spray lightly with nonstick cooking spray. Working one at a time, roll each piece out to about 2 feet long, pressing firmly enough to thoroughly degas the dough. Pop any persistent large bubbles. Taper the ends slightly by pressing more firmly as you roll toward each end.

Shape each pretzel by holding one end in each hand, pulling the ends up and away from you to form a U shape, twisting the ropes around each other once, then folding the ends down toward the bottom of the U. Overlap the ends over the bottom loop and press lightly to secure. Place gently on prepared parchment. Fit 6 pretzels per sheet.

Cover the trays with plastic wrap and proof in a warm spot until visibly risen and very soft to the touch. This takes about 2 hours for 100% sourdough-leavened pretzels or about 45 minutes with added active dry yeast.

Transfer the covered trays to the refrigerator for 30 minutes. Preheat the oven to 450°F.

To prepare the lye solution: Add 1670g cold water to a large glass or stainless steel bowl. Add 70g food-grade lye and stir gently until dissolved. Do not use any aluminum bowls, utensils, or baking sheets; they react with lye.

To prepare the baking soda solution: Combine 1 quart water and 4 teaspoons baking soda in a pot and bring to a rolling boil.

Set up a dipping station: pretzels, then dipping solution, then a wire rack set over a baking sheet, then your prepared baking sheets with pretzel salt nearby.

To dip in lye solution: Place 1 to 2 pretzels top side down in the solution for 30 seconds. Flip with a slotted spoon or spider and remove to the wire rack for 10 to 15 seconds. Transfer to the prepared baking sheet and sprinkle with pretzel salt.

To dip in baking soda solution: Place 1 pretzel top side down in the boiling solution for 5 seconds. Flip and remove directly to the prepared baking sheet. Sprinkle with pretzel salt after every 2 to 3 pretzels, as the surface dries out quickly.

Bake for 18 minutes, rotating the pans after 10 minutes. Allow to cool slightly before serving.