Combine the sourdough starter, both flours and water to a stand mixer. Mix for about 60 seconds with a dough hook until just combined.
Cover and let rest for at least 30 minutes for the autolyse period.
Add salt and honey and mix on low speed (Speed 1) for 1 minute, and then on medium low speed (Speed 2) for about 7 more minutes. Dough should be slightly sticky but it should be able to pass the windowpane test.
Transfer to a generously oiled glass or plastic bowl and let rise for 4-5 hours at room temperature (in your warmest room if you live in a cool climate).
Once the dough ball has doubled in sized, perform 4 “stretch and folds.” This is the miracle that will make your dough light and fluffy. Wait at least 30 minutes between each stretch & fold.
Thirty minutes after the fourth stretch & fold, shape the dough and place it in the final baking dish. If you don’t have an oven-safe Dutch oven, use a cast iron skillet. Line the bottom of the skillet with parchment paper so it doesn’t stick.
Put the finished whole wheat sourdough dough ball into a cool area (50-60 degrees Fahrenheit is best) and let rest overnight. If you live in a warm climate, place it in the refrigerator.
In the morning, let the dough come to just under room temperature (about 65 degrees Fahrenheit). Slash with a serrated knife to allow the steam to escape during baking.Bake at 450 degrees for 30 minutes. Remove from the oven and place on a wire rack. Cover with a damp tea towel for 30 minutes. Remove tea towel and continue letting it rest until it's completely cool (about 1 hour total).
Use a serrated knife to cut as crust may me hard to cut. Toast or serve at room temperature. Store uneaten bread in an airtight container.