Add bread flour (75g), whole wheat flour (25g), and room temperature water (100g) to a clean jar. Mix until no dry flour remains.

Scoop active sourdough-starter (20g) into the mixture and stir until evenly distributed.

Place a rubber band around the jar at the starting height to track rise.

Use a lid set ajar or a cloth secured with a rubber band.

Leave at room temperature (75-78°F) for 8-12 hours. Ready when doubled or tripled, surface is domed, and smells pleasantly sour.

It should be domed, bubbly, and pass the float-test. If not ready, give it more time.

Add warm water (340g) to a large mixing bowl. Add the levain (180g) and stir to disperse.

Add bread flour (400g) and whole wheat flour (50g). Mix with your hand or wooden spoon until no dry flour remains. The dough will be shaggy.

Cover and let rest for 30-60 minutes. This hydrates the flour and begins gluten development.

Sprinkle salt (10g) over the dough. Pinch and fold to incorporate, about 2-3 minutes. The dough will tighten slightly.

Perform 3-4 minutes of slap-and-fold or stretch-and-fold in the bowl until the dough becomes smoother and more cohesive.

Move the dough to a lightly oiled container. Cover.

Every 30-45 minutes for the first 2-2.5 hours (4-5 sets total): wet your hand, stretch one side up and fold over center, rotate 90° and repeat for all four sides.

After folds are complete, let the dough ferment until it has increased by 50-75% in volume.

Look for: visible growth, surface bubbles, dough jiggles when shaken, poke indent fills slowly, edges look slightly domed.

Turn dough onto a lightly floured surface. Using your bench scraper, fold edges toward center, flip seam-side down. Drag toward you to create tension. Rest 20 minutes.

Dust generously with rice flour or a 50/50 blend of bread and rice flour.

Flip dough seam-side up. Fold edges toward center: top, bottom, left, right, and corners. Create a tight package.

Flip seam-side down and use bench scraper to round the loaf, creating tension on the surface.

Place seam-side up in the banneton. Cover loosely with plastic wrap.

Place the covered banneton in the refrigerator.

Let proof for 10-14 hours. The cold slows fermentation dramatically while developing flavor.

Cold dough scores more cleanly and often has better oven-spring.

Place Dutch oven with lid in oven. Preheat to 500°F (260°C) for at least 45 minutes.

Remove banneton from refrigerator. Cut parchment slightly larger than your loaf.

Gently invert banneton onto parchment. The loaf will release seam-side down.

Using a lame or sharp razor, make a decisive slash about ½ inch deep. Options: single ear (curved at 30°), cross, square, or decorative patterns.

Carefully remove hot Dutch oven. Lift loaf by parchment and lower into pot. Cover with lid.

Bake 20 minutes at 500°F with lid on. The trapped steam creates crust development.

Remove lid, reduce to 450°F (230°C), bake 25-30 more minutes until deep mahogany brown.

Internal temperature should reach 205-210°F. Crust should feel hard and sound hollow when tapped.