Place all of the ingredients in a large bowl, reserving 1 cup of the bread flour. Mix until a sticky dough begins to form.
Mix in the remaining cup of flour and knead for 7 minutes, or until the dough becomes soft and elastic, but may still be somewhat sticky to the touch. Depending on the day's humidity, you may need to add a tablespoon or more white flour to achieve a proper sponge. Cover the bowl and let the dough rise until doubled, 45 minutes to 1 hour.
After the first rise, shape the dough into an oblong loaf. Place in a greased 9" x 5" or 10" x 5" bread pan, cover with greased plastic, and let rise until almost doubled, about 60 to 90 minutes.
While the dough is rising, preheat the oven to 375°F When the dough has almost doubled, brush or spray the top with water, dust with pumpernickel or rye flour, and score (slash) the top.
Bake the bread for about 35 minutes, until it sounds hollow when you thump the bottom, or the inside measures 205°F on a digital thermometer. Remove the loaf from the oven and cool it on a rack before slicing.