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  1. Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess.

  2. To make the starter: Combine all of the starter ingredients, mixing just until a cohesive dough forms. Allow it to rest, covered, for 12 to 16 hours at room temperature. When the starter is ready, it will be filled with large holes and bubbles.

  3. To make the dough: Add the water to the starter, and mix until smooth.

  4. Add the flour, yeast and salt, and knead the dough until it's fairly smooth but not necessarily elastic, about 3 minutes by machine, or 5 minutes by hand. (The gluten will continue to develop as the dough rises, so you don't want to develop it fully during the kneading process.)

  5. Place the dough in a lightly greased bowl, cover, and allow the dough to rise at room temperature for 1 1/2 hours. To help develop the gluten and distribute the yeast's food, turn the dough twice during the rising time: gently fold all four sides into the middle, and turn the dough over.

  6. Divide the dough in thirds, and roll each third into a 20"-long rope. Braid the ropes.

  7. Set the braid on a lightly greased or parchment-lined baking sheet, cover with greased plastic wrap and let rise 1 to 1 1/2 hours, until just puffy.

  8. To bake the bread: Preheat oven to 425°F. Gently brush the braid with the beaten egg white mixture and sprinkle generously with sesame seeds.

  9. Bake at 425°F for 25 to 35 minutes or until the loaf is golden and feels lighter when picked up. Remove the braid from the oven and cool on a rack.

  10. Store on the counter, well-wrapped, for 3 days, or freeze for up to 3 months.