How to Make Sourdough Pumpernickel Bread

Day 1: Prepare the Sponge

• In a large mixing bowl, dissolve the instant espresso powder in the room-temperature water. Stir in the active sourdough starter, rye flour, and minced onion.
  294 Grams active starter, 2 Teaspoons Espresso Powder, 227 Grams Water, 213 Grams Whole-Grain Rye Flour, 2 Tablespoons Dried Minced Onion
• Mix until everything is combined. The mixture will be thick.
• Cover the bowl and leave it at room temperature overnight, for up to about 12 hours. The sourdough starter will have time to ferment the mixture and develop flavor before you finish the dough.

Day 2: Finish the Dough

• The following morning, stir the avocado oil, salt, and molasses into the sponge.
  25 Grams Avocado Oil, 2 Teaspoons Salt, 85 Grams Molasses
• Add the all-purpose flour gradually, about one cup at a time, mixing after each addition. Continue until a stiff dough forms and the ingredients are well combined.
  480 Grams All-Purpose Flour
• Depending on your flour and the moisture in your sourdough starter, you may need to adjust the amount of flour slightly.
• Knead and Shape. Turn the dough onto a lightly floured work surface. Knead for 1 to 2 minutes, just until the dough comes together into a cohesive ball with no dry flour remaining.
• Rye dough can be naturally tacky, so resist the temptation to add too much extra flour. Lightly oiling your hands can make the dough easier to handle.
• Shape the dough into a log that fits your cast iron bread pan.
• Let the Dough Rise. Grease your cast iron bread pan and place the shaped loaf inside. The pan should be cold rather than preheated.
• Cover the pan and let the dough rise for approximately 2 to 4 hours, or until the loaf reaches the top edge of the pan.
• The rising time will depend on the strength of your starter and the temperature of your kitchen. Use the dough's appearance as your guide rather than relying on the clock alone.
• Bake the Bread. Preheat your oven to 425°F.
• Once the dough has risen, transfer the covered cast iron bread pan to the oven. Bake covered for 30 minutes to help retain moisture during the initial baking stage.
• Carefully remove the cover and continue baking for another 15 to 20 minutes, until the crust is deeply browned and set.
• Because ovens and cast iron pans vary, begin checking the loaf toward the earlier end of the uncovered baking time.
• Cool Before Slicing. Remove the bread from the pan and transfer it to a wire rack.
• Allow the loaf to cool completely before slicing. This gives the interior time to finish setting and makes it easier to cut neat slices without compressing the bread.