How to Make It
In a medium bowl, combine 1 2/3 cups of the unbleached flour with 1/2 cup of warm water and 1/4 teaspoon of the yeast and stir until a shaggy dough forms. Cover with plastic wrap and let stand overnight at room temperature.
In a large bowl, pour the boiling water over the cereal; stir until moistened. Let stand at room temperature until cool.
Meanwhile, in a large bowl, combine the remaining 2 1/4 teaspoons of yeast with 1/4 cup of lukewarm water (90° to 110°) and let stand until the yeast is dissolved, about 5 minutes. Add the starter to the bowl along with the remaining 1 1/2 cups unbleached flour, the whole wheat flour, honey and salt. Add 2 1/4 cups of lukewarm water (90° to 110°) and stir until a soft, sticky dough forms. Turn the dough out onto an unfloured work surface and, alternating between using a dough scraper and your hands, knead, pull and stretch the sticky dough until smooth, about 5 minutes. Do not add more flour. Return the dough to the bowl and let rest for 15 minutes.
Knead the dough 4 times in the bowl and let rest for 15 minutes. Knead the dough again 4 times and let rest for 15 minutes longer. Turn the dough out onto an unfloured work surface and knead in the cooled cereal until evenly incorporated and the dough is firm and smooth, about 5 minutes. Form the dough into a large ball and return it to the bowl. Cover and let rise until billowy and doubled in bulk, about 1 hour.
Punch down the dough and let rest for 30 minutes. Turn the dough out onto a lightly floured work surface. Divide it in half and form each half into a smooth ball. Transfer each ball to a lightly floured baking sheet and cover with an inverted large bowl. Let the dough rise in a warm, draft-free spot until nearly doubled in bulk, about 45 minutes.
Meanwhile, set a pizza stone on the bottom shelf of the oven and preheat to 500°, allowing 45 minutes for the stone to heat. Slide both loaves onto the stone and bake for 10 minutes. Lower the oven temperature to 425° and bake for 35 minutes longer, or until the loaves are deep brown and sound hollow when tapped on the bottom. Alternatively, bake the loaves directly on the baking sheets. Transfer the bread to a wire rack and let cool overnight.