Pumpernickel flour, sometimes labeled dark rye flour, is a coarse, especially dark, flavorful form of rye flour. To make a pumpernickel loaf, follow the directions for rye bread (opposite), but substitute pumpernickel flour for the rye flour. Pumpernickel bread is best made with a natural starter, but you can also make it with yeast. Use a stand mixer for this dough. It is quite sticky and unpleasant to make by hand.