Mix Ingredients: In a large bowl, combine the sourdough starter, water, flours, and salt. Stir until a shaggy dough forms.
Rest (Autolyse): Cover with a damp towel and let sit for 30 minutes to hydrate the flour.
Stretch & Fold: Every 30 minutes for 2 hours, wet your hands and stretch the dough upward, then fold it over itself (4 folds per session).
First Rise: Let the dough ferment at room temperature for 6-12 hours (or until doubled in size).
Pre-shape: Turn the dough onto a floured surface, gently shape into a round, and rest for 20 minutes.
Final Shape: Tighten the dough into a boule (round) or batard (oval). Place seam-side up in a floured banneton or bowl lined with a towel.
Second Rise: Refrigerate for 12-24 hours (cold proof) OR proof at room temp for 1-2 hours.
Preheat: Place a Dutch oven in the oven and preheat to 475°F (245°C) for 30 minutes.
Score & Bake: Turn the dough onto parchment paper, slash the top with a razor, and transfer to the Dutch oven. Bake covered for 25 minutes, then uncovered for 20 minutes until deep golden brown.
Cool: Let the bread rest on a wire rack for 1 hour before slicing.
