• 1/2 teaspoon active dry yeast (not rapid-rise)
  
• 1 cup cool water
  
• 1 cup bread flour
  
• 1 cup whole wheat flour

Dissolve yeast in water in a medium-sized bowl. With a rubber spatula, mix in flours to create a stiff, wet dough. Cover bowl with plastic wrap; let sit at room temperature for at least 5 hours, preferably overnight.

DOUGH

• 1/2 cup rye flour
  
• 1 cup whole wheat flour (whole wheat graham flour preferred)
  
• 1/4 cup wheat germ
  
• 1 1/3 cups warm water
  
• 2 tablespoons molasses
  
• 2 teaspoons table salt
  
• 2 1/4 cups bread flour, or as needed
  
• Coarse cornmeal for sprinkling on peel (optional)

If you are kneading by hand, place the sponge and all dough ingredients, except the bread flour and cornmeal, in a large bowl. Stir mixture with a wooden spoon, about 5 minutes. Using the spoon, work in reserved bread flour and turn dough out onto a floured surface. Knead for 10 minutes, adding flour in l tablespoon increments only when absolutely necessary, being careful not to incorporate more than 1/4 cup of additional flour. The dough will remain sticky but become smooth. Transfer dough to a large, lightly oiled bowl. Cover with plastic wrap; let rise until tripled in size, at least 2 hours.

ASSEMBLY

Turn dough out onto a lightly floured surface. Lightly dust hands and top of dough with flour. Lightly press dough into a disk. Fold all four sides toward the center, overlapping edges slightly. Transfer dough, smooth side down, to a colander or basket lined with heavily floured muslin or a tea towel. Tent loosely with a large sheet of aluminum foil; let rise until almost doubled in size, at least 45 minutes.

As soon as dough begins to rise, adjust oven rack to low-center position and arrange quarry tiles to form an 18 x 12 inch surface (or larger). (You can also use a pizza stone.) On lowest oven rack, place a small baking pan or cast-iron skillet to hold water. Heat oven to 450 degrees.

Liberally sprinkle cornmeal over entire surface of a baker's peel (or place a large sheet of heavy-duty parchment paper on the baker's peel). Invert risen dough onto peel and remove muslin or tea towel. Use scissors or a serrated knife to cut three slashes on top of dough.

Slide dough, with a quick jerk, from peel onto tiles. Carefully pour 2 cups hot water into heated pan or cast-iron skillet. Bake until an instant-read thermometer, when inserted in bottom of bread, registers 205 to 208 degrees and crust is very dark brown, 35 to 40 minutes, turning bread after 25 minutes if not browning evenly. Turn oven off, open door, and let bread remain in oven 10 minutes 1onger. Remove from oven and let cool on a cake rack to room temperature before slicing, about 2 hours. To crisp the crust, heat in a 450 degree oven for 10 minutes.

Makes 1 Large Loaf