01 - In a large mixing bowl, combine the sourdough starter, water, and brown sugar. Stir until completely dissolved.
02 - Add bread flour, whole wheat flour, cinnamon, nutmeg, ginger, and salt to the bowl. Mix until a sticky, shaggy dough forms.
03 - Fold in the grated carrots, raisins, and nuts until evenly distributed throughout the dough.
04 - Knead the dough gently for 3-4 minutes by hand or with a dough hook attachment until just combined.
05 - Cover the bowl with a clean towel and let the dough rest for 30 minutes to allow flour hydration.
06 - Perform 3-4 sets of stretch and folds every 30 minutes over the next 2 hours to develop gluten structure.
07 - Cover and let the dough rise at room temperature for 4-6 hours until doubled in size.
08 - Shape the dough into a boule or batard, then place in a parchment-lined banneton or bowl for proofing.
09 - Cover and refrigerate overnight for 8-10 hours to develop flavor through slow fermentation.
10 - Preheat the oven to 450°F with a Dutch oven inside to ensure proper oven spring.
11 - Turn the dough onto parchment paper, sprinkle with oats and seeds if desired, and score the top with a sharp knife.
12 - Carefully transfer the dough into the preheated Dutch oven. Bake covered for 25 minutes to trap steam.
13 - Remove the lid and continue baking for 20 minutes until the crust is golden brown and crispy.
14 - Transfer the bread to a wire rack and let cool completely before slicing to ensure proper texture.