Step 1

The sponge: Pour the cup of starter into a large mixing bowl. Add the warm water and 3 cups of flour. Beat vigorously with a wooden spoon. Cover this sponge with plastic wrap and put it aside to work. This period can be very flexible, but allow at least 2 hours and up to 8 hours. A longer period (at a lower temperature) will result in a more sour flavor.

Step 2

The dough: After the sponge has bubbled and expanded, remove the plastic wrap. Blend the salt and one cup of flour. Stir the flour and salt into the sponge then add more flour, a little at a time until the dough comes together. Turn it out onto a floured board and knead it for 3 to 4 minutes. Give the dough a rest while you clean out and grease your bowl. Continue kneading for another 3 or 4 minutes, adding extra flour as needed, until the dough is smooth and elastic. Add only enough extra flour to keep the dough from sticking. Place the dough in the bowl, turn it once to grease the top, cover, and let it rise until doubled (1 to 2 hours).

Step 3

Shaping and Baking: Turn the dough out, then divide in half. Shape each half into a loaf, and place on a lightly greased, cornmeal-sprinkled baking sheet. Cover, and let rise until doubled (this can take up to 2 hours). Remove the cover, slash the tops, and bake in a preheated 450 degree oven for approximately 20 minutes, until golden brown. Turn the oven off, crack the door, and leave the loaves in for another 5 minutes. Remove loaves to a cooling rack and let cool completely before slicing.