Dark, tangy, and dense, traditional pumpernickel bread is made from rye flour mixed with a little wheat flour; several sourdough fermentations are what give it its tangy flavor. Loaves of true pumpernickel undergo a long, slow bake (up to 24 hours); the dark color comes from a browning reaction that takes place in the dough during that time. (Less-traditional pumpernickel bread relies on molasses for its color and flavor).
Pumpernickel is often baked in a narrow, rectangular loaf; the thin, square slices are a great way to fill out a weeknight supper, and they are the traditional accompaniment to cold-weather sausage dishes like bratwurst.
