San Francisco Sourdough Bread

Steps

1. Mash the grapes thoroughly and place in a loosely-covered container. Allow to stand at room temperature for 48 hours.
2. Strain off the fermented juice and discard the pulp.
3. Add warm water to the juice to make 470 ml (450 ml).
4. Stir in the flour, and leave at room temperature overnight.
5. Replenish with 470 ml of warm water and 470 ml of flour daily if the starter is kept at room temperature. If refrigerated, replenish twice a week.
6. In a glass measuring cup, sprinkle the dry yeast onto the surface of 4 tablespoons of the warm water and allow to stand until it becomes foamy.
7. In a bowl, combine the rest of the water with the sourdough starter.
8. Add 240 ml of the flour. Stir until the dough starts to form and then add the yeast mixture. Mix for 5 minutes.
9. Add the remaining flour and the salt. Knead the dough until it is soft and elastic, 10 minutes or more.
10. Place the dough in a greased bowl and cover with a damp cloth. Let rise in a warm place (ca. 80°F/27°C to 90°F/32°C) until doubled.
11. Punch down the dough and shape it into a round loaf. Place the loaf on a greased and cornmeal-dusted sheet pan.
12. Let the loaf rise in a warm place, covered with a damp cloth, until it has doubled in size.
13. Brush the loaf with beaten egg white and score the top of the loaf in a criss-cross pattern with a sharp knife.
14. Bake at 450°F (230°C) with a pan of boiling water under the oven rack for 10 minutes.
15. Reduce the oven temperature to 375°F (190°C), remove the water and continue baking until the bread is well browned (about 35–45 minutes).
16. Cool on a rack.