A classic whole wheat sourdough loaf! This bread uses 30% whole wheat flour, for a loaf that's more complex and flavorful than your standard sourdough, while still being easy to work with and getting a good rise. Makes 1 loaf.
Combine the water and starter in a large bowl. Add the flours and salt and mix until no dry bits of flour remain - mix with your hands when it becomes too difficult to mix with a fork or spoon. Cover and let rest for 30-60 minutes, then do a round of stretch and folds. Let rise covered until doubled in size, about 8-12 hours.
Shape the Dough + Second Rise
Turn the dough out onto a lightly floured surface. Press it into a disc, then fold the right side into the middle. Fold the left side into the middle, over the previously folded side. Then fold the top (the side farthest from you) into the middle. Finally, stretch the side closest to you toward yourself and fold it over the previously folded side. Turn the dough seam side-down and use cupped hands to pull it toward yourself, building tension in the dough. Turn it seam side up into a prepared proofing basket or towel-lined bowl.Cover and let rise for 1-2 hours at room temperature, or up to 48 hours in the fridge.
Baking
Preheat oven to 450 degrees. Turn the shaped loaf out onto a piece of parchment paper and score the top of it. Place the loaf - on the parchment paper - into a Dutch oven and cover. Bake for 20 minutes, then remove the lid, reduce the oven temperature to 400, and bake for another 30 minutes. Cool bread on a wire rack for at least an hour before slicing.