01 - In a large bowl, combine the bread flour, whole wheat flour, and water until just incorporated. Cover the bowl and let rest for 1 hour to hydrate the flour.
02 - Add the active sourdough starter and sea salt to the dough. Mix by hand or spatula until fully integrated and no dry flour remains.
03 - Cover and let ferment at room temperature for 4-5 hours. Every 30-45 minutes, perform a stretch and fold: grab one edge of the dough and pull it upward, then fold it over the center. Repeat on all four sides. Complete 4 sets of stretches and folds throughout fermentation.
04 - Turn the dough onto a lightly floured surface. Gently shape it into a round boule. Cover with a towel and let rest for 20 minutes to relax the gluten.
05 - Shape the dough into a tight round loaf, creating surface tension. Place seam side up in a well-floured proofing basket or bowl lined with a floured towel.
06 - Cover and let rise at room temperature for 2-3 hours until increased by about 50%. Alternatively, refrigerate overnight for 12-16 hours for enhanced sour flavor development.
07 - Position a Dutch oven or heavy oven-safe pot with lid in the oven. Preheat to 480°F for at least 30 minutes to thoroughly heat the vessel.
08 - Gently invert the dough onto parchment paper. Use a sharp blade or bread lame to score the surface with a swift, decisive cut. Transfer to the preheated pot, cover, and bake for 20 minutes. Remove lid, reduce temperature to 430°F, and bake for another 25 minutes until deep golden brown with a hollow sound when tapped.
09 - Remove bread from pot and transfer to a wire rack. Cool completely for at least 2 hours before slicing to ensure proper crumb structure.