• Leaven Ingredients
• 100 g water, 90° F
• 25 g sourdough starter, fed 10-12 before beginning leaven
• 100 g bread flour

• Bread Ingredients
• 275 g water, 92° F
• Ripe leaven
• 400 g bread flour
• 50 g whole wheat flour
• 12 g salt

Build the leaven: mix water (100 g) and sourdough starter. Add flour (100 g) and mix until well combined. Cover bowl and leave sit at room temperature for 10-12 hours. Leaven should be bubbly and grow in size.

Mix dough: mix leaven with water (275 g) until leaven is dissolved. Add bread and wheat flours and salt. Mix as much as possible with a stout spoon. Then mix (fold & squeeze) by wet hand until no dry spots remain.

Bulk fermentation: let dough ball rest 30 minutes. Do a series of strengthening folds. Round into ball. Let rest 30 minutes. Do strengthening folds. Round into ball. Let rest in warm place (90-95° F) for 2 hours.

Shaping dough: Turn out dough onto lightly floured work surface. Perform at least 4 book folds, rotating 90° between folds. Flip dough and form into a ball with some surface tension. Place seam side up in floured proofing basket. Cover with floured tea towel.

Proofing: place in warm spot for 60-90 minutes. Dough should increase in size about 60%. Poke dough to see if done proofing, it should slowly bounce back.

Baking: preheat oven to 450° F. with baking cast iron pot in oven. Remove heated cast iron. Turn dough out from proofing basket so that it ends up seam side down in the pot. Score dough 5-6 times. Bake covered for 15 minutes. Remove cover and bake for an additional 30 minutes.

Leaven: 12 hours
Fermentation/proofing: 4 hours 30 minutes
Baking: 45 minutes

Source: Brian Lagerstrom