Sourdough Pumpernickel Bread (From King Arthur Flour)
1 1/3 cups active (fed) sourdough starter, any variety is fine
1 cup room temperature black coffee or potato water (water in which potatoes have been boiled)
2 cups pumpernickel flour
1/2 cup chopped onion
2 tablespoons vegetable oil
2 teaspoons salt
1/4 cup molasses
4 cups unbleached all-purpose flour
To make the sponge: Measure the starter into a bowl. Add the coffee or potato water, pumpernickel, and onion. Stir together, cover, and let bubble away at room temperature overnight.
To make the dough: The next day, stir the oil, salt and molasses into the sponge. Stir in the flour 1 cup at a time, until the dough comes together.
Turn the dough out onto a lightly floured surface and knead, adding only enough additional flour to keep it from sticking to your hands.
There are a number of ways to shape this dough. Make one large round loaf, which you'll place on a pumpernickel-sprinkled baking sheet. Or make two smaller versions of the same thing. Or place the entire amount of dough into a large (10" x 5") loaf pan. Or divide it in half, and use two smaller (8 1/2" x 4 1/2") loaf pans.
Cover the loaves with a piece of lightly greased plastic wrap. Let them rise in a draft-free spot. You can predict the amount of rise somewhat by the temperature of the space where they're rising: at 55°F to 60°F, they'll probably take 3 to 5 hours to rise; at 65°F to 70°F, 2 to 4 hours.
A short time before the loaves have doubled in size, place them in a preheated 350°F oven; they'll continue to rise during the first 15 minutes of baking.
Bake two smaller loaves for about 35 minutes; one large loaf will bake for about 45 minutes.
The loaves are done when the centers measure 200°F when measured with an instant-read thermometer. Remove from the oven and put on a rack to cool before slicing.