Makes one 3-pound round loaf

After kneading the dough, turn it out onto a work surface. Press it to flatten, sprinkle on walnuts and fold the dough over on itself a few times. Knead for a minute to be sure walnuts are evenly incorporated. Turn dough into a large bowl, cover, and let rise for 1 1/2 hours until double in bulk. Fold the dough down on itself a few times and then cover again and let rise for 45 minutes before deflating and shaping.

To shape dough into a boule, fold the fully risen dough over on itself a few times, turn it out onto a work surface, and gather it together gently between your rounded palms. Work the dough around, using the unfloured work surface to create tension, until you have a smooth ball. Sprinkle the inside of a banneton or towel-lined colander with rice flour and turn the walnut dough over into it; the dough's smooth side will be down. Cover and let rise in a warm place for 1 1/2 hours. Position a rack in the lower third of the oven, line it with quarry tiles and preheat oven to 450°F. Put a cast-iron skillet on the floor of the oven if it is a gas oven, or directly on the heating element if it is electric. About 2 minutes before the loaf goes into the oven, open the oven door, stand back, and pour 1 cup of warm water into the hot skillet. Immediately close the oven door to trap the steam. Invert the bread onto a floured peel and, using a single-edge razor blade, quickly slash the bread by cutting a cross in the center and making one short slash from the center out in each of the resulting quadrants. Slide the bread onto the hot quarry tiles and turn oven temperature down to 400°F. Bake 40 to 50 minutes, or until deeply browned and the internal temperature registers 200°F. Remove to a rack to cool completely before cutting.