01 - In a large bowl, combine the bread flour, whole wheat flour, and water. Mix until just combined. Cover the bowl and let rest for 1 hour to hydrate the flour.
02 - Add the sourdough starter and sea salt to the dough. Mix by hand or using a spatula until fully incorporated and the dough begins to develop structure.
03 - Cover the bowl and let ferment at room temperature for 4 to 5 hours. Every 30 to 45 minutes, perform a stretch and fold by lifting one edge of the dough and folding it over the center. Repeat this process 4 times around the bowl to build strength.
04 - Turn the dough onto a lightly floured work surface. Gently shape it into a round loaf without degassing too much. Cover and let rest for 20 minutes to relax the gluten.
05 - Shape the dough into a tight round loaf, creating surface tension. Place the loaf seam side up in a well-floured proofing basket or lined bowl.
06 - Cover and let rise at room temperature for 2 to 3 hours until visibly puffy. For enhanced sour flavor, refrigerate overnight for a cold proof.
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 the dough onto parchment paper. Score the surface with a sharp blade or bread lame in your desired pattern. Transfer to the preheated pot, cover with the lid, and bake for 20 minutes. Remove the lid, reduce temperature to 430°F, and continue baking for 25 minutes until deep golden brown.
09 - Remove the bread from the pot and transfer to a wire rack. Allow to cool completely for at least 1 hour before slicing to ensure proper crumb structure.