San Francisco Sourdough Bread

Step 1
Combine 1 cup flour, sugar, salt, and yeast in a large bowl. Add warm milk and margarine. Stir in starter. Mix in remaining 3 3/4 cups flour gradually; you may need to add more flour depending on the climate.

Step 2
Turn dough out onto a floured surface and knead for 8 to 10 minutes. Place dough into a greased bowl, turn once to oil surface, and cover. Allow to rise until doubled in volume, about 1 hour.

Step 3
Punch down dough; cover and let rest for 15 minutes. Divide dough in half and shape into 2 loaves. Place loaves on a greased baking pan. Allow to rise until doubled in volume, about 1 hour.

Step 4
Preheat the oven to 375 degrees F (190 degrees C)

Step 5
Stir together egg and water in a small bowl until well combined. Brush over the tops of loaves, then sprinkle with onion.

Step 6
Bake in the preheated oven until loaves are golden brown and cooked through, about 30 minutes. An instant-read thermometer inserted into the center of a loaf should read 190 degrees F (88 degrees C).