Place in a medium bowl:

Feed the starter with:

Stir until smooth. Combine and sprinkle over the top of the starter:

Cover tightly with plastic wrap and let ferment until the starter has risen and created a network of cracks in the flour sprinkled over it, 4 to 5 hours.

Mix until smooth and then stir in:

The dough should be neither very dry nor very wet. If necessary, add a little more flour or water to adjust the consistency. Let the dough rest for 20 minutes. Turn the dough out onto a lightly floured work surface and knead until smooth and pliable, working in more all-purpose flour if it is too sticky (the dough will be tacky, but it should not stick aggressively to your hands). Divide the dough into 2 equal pieces, and shape into rounds. Place the loaves on a greased baking sheet, cover loosely with a cloth, and let rise until increased but not doubled in bulk. A fingertip pressed gently into the dough should leave an imprint that does not spring back right away. This should take 3 to 4 hours.

Position racks in the center and lower third of the oven. Preheat the oven to 425°F. Place a metal baking pan or cast-iron skillet on the lower rack.

Score the loaves if desired, place on the center rack in the oven, and immediately pour 1 cup hot water into the baking pan or skillet. Bake until the internal temperature of the loaves reaches at least 110°F, 50 to 60 minutes. To further set the crust, turn the oven off and let the loaves remain in the oven for 10 minutes. Transfer to a rack to cool completely.