Artisan Boule

Poolish: In a small bowl, stir together yeast, water, and bread flour until it has the consistency of thick pancake batter. Cover with plastic wrap and let stand at room temperature 8 to 12 hours.

Dough: In a liquid-measuring cup, stir together yeast and water until yeast is dissolved. Place poolish and both flours in the bowl of an electric mixer fitted with the dough hook attachment. Add yeast mixture and mix on medium-low speed until a sticky dough forms, about 2 minutes. Add salt and increase speed to medium-high; mix until dough is smooth and elastic, and cleans sides and bottom of bowl, about 9 minutes. Scrape dough onto a lightly floured surface and gather into a ball with oiled hands, then transfer to a large oiled bowl. Cover with plastic wrap and let rise in a warm spot until doubled in bulk, 1 1/2 to 2 hours.

On a lightly floured surface, pat dough into a 12-by-10-inch rectangle with one short side parallel to edge of work surface. Fold dough into thirds, aligning edges carefully. Fold dough in half. This completes one turn. Flip dough so seams are facing downward and gently shape into a ball. Return to oiled bowl and cover with plastic wrap. Let rise in a warm spot until doubled in bulk, about 1 hour.

Preheat oven to 450 degrees with a pizza stone on center rack, and a cast-iron skillet on rack below. Be sure to remove any additional racks from oven.

Place a sheet of parchment on a pizza peel or unrimmed baking sheet and lightly dust with flour; set aside. On a lightly floured surface, repeat folding process to complete a second turn. Gather corners of dough and pinch together, then flip dough over, shaping into a tight ball. Transfer dough, seam-side down, to prepared pizza peel, adjusting shape as needed. Loosely cover with oiled plastic. Let stand in a warm spot until puffy and full of air, about 45 minutes.

Lightly dust surface of bread with flour. Using an oiled razor blade or a very sharp knife, score surface in a decorative pattern. Working as quickly as possible, carefully slide parchment from peel onto pizza stone. Pull just enough of heated skillet out of oven to add ice before closing oven door. Bake until bread is deep golden brown and an instant-read thermometer inserted into center reads 205 degrees, 45 to 50 minutes. Transfer to a wire rack and let cool completely before serving.