01 - In a large bowl, combine bread flour, whole wheat flour, and water. Mix until just incorporated, then cover and let rest for 1 hour to develop gluten structure.
02 - Add sourdough starter and sea salt to the autolysed dough. Mix by hand or spatula until fully incorporated and the dough begins to develop elasticity.
03 - Cover the bowl and let ferment at room temperature for 4 to 5 hours. Perform stretch and folds every 30 to 45 minutes, repeating 4 times total to strengthen the dough.
04 - Turn dough onto a lightly floured surface. Gently shape 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 to 3 hours until increased by about 75%. For enhanced sour flavor, refrigerate overnight for 12 to 16 hours.
07 - Position a Dutch oven or heavy pot with lid in the oven. Preheat to 480°F for at least 30 minutes to ensure proper heat retention.
08 - Gently invert dough onto parchment paper. Score the surface with a sharp blade or lame. Transfer to preheated pot, cover with lid, and bake at 480°F for 20 minutes. Remove lid, reduce temperature to 430°F, and bake 25 minutes until deep golden brown and internal temperature reaches 200°F.
09 - Remove bread from pot and transfer to a wire rack. Cool completely for at least 2 hours before slicing to allow the crumb to set properly.