In a large mixing bowl, combine the bread flour and whole wheat flour with 280g of the warm water. Mix with a dough scraper or your hands until no dry spots remain and a shaggy dough forms. Cover the bowl and let it rest for 30-60 minutes (autolyse). This allows the flour to fully hydrate.

After the autolyse, add the active sourdough starter and the fine sea salt to the dough. Pour the remaining 20g of water over the salt. Mix vigorously for 5-7 minutes, incorporating the starter and salt until fully combined and the dough starts to develop some elasticity. It will be sticky.

Cover the bowl and let the dough rest for 30 minutes. Begin the first set of 'stretch and folds'. With wet hands, gently grab a portion of the dough, stretch it upwards, and fold it over itself. Rotate the bowl a quarter turn and repeat this motion 3-4 times until all sides have been stretched and folded. Repeat this process every 30-45 minutes for a total of 4 sets over 2-3 hours.

After the initial stretch and folds, gently turn the dough out onto a lightly floured surface. Flatten it into a rough rectangle. Sprinkle the diced pepperoni, shredded cheese, garlic powder (if using), and dried oregano (if using) evenly over the surface. Fold the dough over on itself a few times to gently incorporate the inclusions. Be careful not to tear the dough excessively. Return the dough to the bowl, cover, and allow it to continue bulk fermenting for another 1-2 hours, or until it has increased in volume by about 30-50% and feels airy.

Lightly flour your work surface. Gently tip the dough out onto the surface. Using a dough scraper and wet hands, gently preshape the dough into a loose round or rectangle. Allow it to rest, uncovered, for 20-30 minutes to relax the gluten.

Dust your proofing basket (banneton) generously with rice flour. Gently shape the dough into your desired final shape (boule or batard). For a boule, pull the edges of the dough into the center, then flip it over and gently cup and pull towards you to create surface tension. For a batard, fold into thirds like a letter, then roll tightly into an oval.

Carefully place the shaped dough, seam-side up, into the floured banneton. Cover the banneton with a plastic bag or plastic wrap and refrigerate for 12-16 hours (or up to 24 hours). This slow, cold proof develops flavor and makes the dough easier to handle.

Preheat your oven to 475°F (245°C) with your Dutch oven inside for at least 45-60 minutes. Carefully remove the hot Dutch oven from the oven. Gently invert the cold dough from the banneton onto a piece of parchment paper. Score the top of the dough with a sharp knife or lame.

Carefully lift the dough by the parchment paper and place it into the hot Dutch oven. Cover with the lid and bake for 25 minutes. Remove the lid and continue to bake for another 20-25 minutes, or until the crust is deep golden brown and the internal temperature reaches 200-210°F (93-99°C).

Carefully remove the bread from the Dutch oven and transfer it to a wire rack to cool completely for at least 1.5-2 hours before slicing. Slicing too early will result in a gummy texture.