Prepare the starter: Stir the yeast into the warm water and let it stand for 10 minutes, until creamy.

Add the flour to the starter and stir with 100 strokes of a wooden spoon, or with the paddle of an electric mixer for 1 minute.

Cover the starter with plastic wrap and let rise until tripled, 6 hours to overnight.

Prepare the dough: Stir yeast into the warm water and let it stand for 10 minutes, until creamy.

Add the room temperature water and the starter to the yeast mixture.

Stir vigorously or squeeze the mixture between your fingers to break the starter up.

Stir in the flours, half at a time, until thoroughly mixed.

Knead dough on floured work surface until firm and resilient, 8 to 10 minutes.

Place dough in a lightly oiled bowl, cover tightly with plastic wrap, and let rise until doubled, 1 to 1 1/2 hours.

Turn the dough out onto a floured surface, and punch it down.

Shape the dough into a large round loaf, or 2 oval loaves.

Place the loaf (ves) on a cornmeal-sprinkled peel or an oiled baking sheet.

Dust the top (s) lightly with flour, cover with a lightly dampened towel, and let rise until doubled again, 45 to 60 minutes.

Preheat oven to 450F.

Score top of loaf (ves) with a sharp knife or razor in a "tic-tac-toe" pattern and slide onto a baking sheet sprinkled with cornmeal.

Bake 15 minutes, then turn the heat down to 400F& bake 20 minutes for the smaller loaves, and 25 to 30 minutes for the large loaf.

Loaf is done when they sound hollow when tapped.

Cool on a rack.