Whisk the starter into the water to disperse. Add the flour and mix until no dry bits remain; cover and rest 30 minutes
Sprinkle in the salt. Pinch and fold until fully incorporated and the dough tightens slightly
Over the first 2 hours, perform gentle stretch-and-folds every 30 minutes. During the second set of folds, scatter the cranberries and walnuts over the dough and fold to distribute without tearing. Continue bulk until the dough has risen ~50–75%, feels jiggly, and shows domed edges
Lightly flour the surface, turn out the dough, and pre-shape into a round. Cover and rest 20–30 minutes
Shape into a tight boule or batard. Place seam-side up in a well-floured banneton (rice flour helps prevent sticking)
Cover and refrigerate 12–16 hours for flavor and easy scoring
Preheat a Dutch oven to 476°F for 30–45 minutes. Turn the dough onto parchment seam-side down, score, and load
Bake 20 minutes covered, then 20 minutes uncovered until deeply browned
Cool at least 1–2 hours before slicing
Enjoy!
Notes
Hydration: Base is 70% (350 g water to 500 g flour). With a 100% hydration starter, effective hydration is ~73%.
Flour: Bread flour or strong AP both work; adjust with an extra coil fold if the dough feels slack.
Cranberries: Dried are easiest; if using fresh, reduce to 90–100 g and pat very dry.
Walnuts: Toast first and cool to minimize purple tint; some light coloring is normal.
Storage: Keep cut-side down on a board for 24 hours, then bag or freeze slices.