The toughest part of bread making, in my opinion, is working out the timing throughout the day. For this recipe, the sponge can be made the night before and set on the counter until the following mid-day when the dough can be made, (optionally, be left to rise for another 2-4 hours), then shaped and left to rise 2 hours before baking 25 minutes for dinner.
1 cup sourdough starter
1 1/2 cups warm water
5 1/2 – 6 1/2 cups flour
1 tablespoon sugar
1 teaspoon baking soda
cornmeal or polenta to sprinkle on pans
boiling water for oven
Make the Sponge: Mix well your sourdough starter and pour one cup into a large mixing bowl. (With the remaining starter, add one cup flour and one cup water to replenish it.) To the one cup of starter, add 1 1/2 cups of warm water and 3 cups of flour. Mix. Cover the bowl with a towel. It will come to life as it sits on the kitchen counter 2-24 hours.
Making the Dough (& an Optional Rise: Blend salt, sugar, & baking soda into 2 cups of flour. Mix this into the sponge.When the dough begins to hold together, turn it out onto a floured board and knead for 3-4 minutes. Add flour as needed to make a fairly stiff dough. When you have accomplished that, give the dough a rest while you clean out the bowl and grease it. Transfer the dough to the greased bowl, cover with a clean cloth, & let it sit on the counter to rise for 2-4 hours. This rise is optional. However, adding it will create a more sour flavor in your bread.
Shaping: Punch down the risen dough and shape it into two long (or round) loaves. Place them on a baking sheet or in a cast iron skillet sprinkled with cornmeal or polenta. Let the shaped loaves rise on their pans for about 2 hours. Towards the end of the rising period, place a deep dish baking pan on the bottom rack and preheat your oven to 450 degrees.
Baking: Just before it is time to bake, use a sharp knife to make a few diagonal slashes, a few inches long and 1/4 inch deep, in the top of each loaf. Brush each loaf with cold water. Pour 2-3 cups of water in the hot pan on the bottom rack of the oven and put the loaves in the steamy oven on a rack just above the steam. Bake for about 25 minutes. When you remove the loaves from the oven, the crusts will be very hard. Soon, they will be soft and chewy, and a pleasure to eat with fresh butter.
Recipe from The King Arthur Flour 200th Anniversary Cookbook