10:00 PM – Starter Build: In a small glass jar, add your 5g of starter culture to 35g of water and whisk together cleanly. Stir in 30g of all-purpose or bread flour and 5g of rye flour. Mix thoroughly, cover loosely, and let it sit at room temperature 74–78°F (23–26°C) overnight for 8 to 10 hours until the starter reaches its peak and at least triples in volume.

5:00 PM – The Core Autolyse: In your stand mixer bowl, combine the 270g of bread flour, 30g of whole wheat flour, and 207g of main water. Mix thoroughly with a spoon just until all dry flour patches entirely disappear. Cover tightly and let it rest on your counter for 1 full hour. During this autolyse, the flour proteins absorb the water completely, becoming fully hydrated to naturally kickstart strong gluten bonds.

6:00 PM – Sourdough Starter Integration: Add 60g of your active overnight starter peak directly into the autolysed dough. Turn your mixing machine on low speed for 2 to 3 minutes (or use a KitchenAid mixer on speed 3 for 3 to 4 minutes) until the starter is completely incorporated. Cover and let rest for 30 minutes.

6:30 PM – Bassinage & Salt Incorporation: Add your 6g of salt along with the remaining 30g of cold bassinage water into the bowl. This secondary hydration step helps tighten up the developing gluten network. Mix on low speed for 2 to 3 minutes (or on a KitchenAid on speed 3 for 5 to 6 minutes) until the extra liquid is fully absorbed. The dough will pull together cleanly but should remain sticky on the bottom of the bowl. Cover and let rest for 30 minutes at 74–78°F (23–26°C). The Hot Cocoa Blend Setup: While the dough rests, whisk together the 15g of cocoa powder, 15g of dry milk powder, and 15g of sugar in a small bowl until completely uniform.

7:00 PM – The Hot Cocoa Lamination: Spray your clean work surface lightly with water and wet your hands. Gently tip the sticky dough out and stretch it out as thin as possible across the table without tearing the delicate matrix. Sprinkle your prepared cocoa powder, dry milk, and sugar mixture evenly over the entire surface of the sheet.

The Spritzer Hydration: Take your water spritzer and spray a fine mist of water directly over the dry cocoa layer. (The Moisture Hack: Because cocoa powder and dry milk powder are highly absorbent, they will ruthlessly suck hydration away from the dough and ruin the texture if left dry; misting them ensures the dough matrix remains soft and supple). Fold the dough cleanly over onto itself into a neat package, return it to your bulk proofing container, and let rest for 45 minutes.

7:45 PM – 1st Stretch & Fold: Wet your hands slightly. Lift one side of the dough up cleanly from the container edge and fold it directly over the center. Repeat this action for all four quadrants of the dough mass to build structured vertical strength. Cover and let rest for 45 minutes.

8:30 PM – 2nd Stretch & Fold: Execute your second structured round of quadrant folds to continue organizing the expanding gluten network. Cover and let rest for 45 minutes.

9:15 PM – 3rd Stretch & Fold: Execute the third and final stretch-and-fold round. Cover and let the dough proof completely untouched for 30 minutes at a warm 76–80°F (24–27°C). The dough should look visibly lighter, show distinct dark marbling and surface bubbles, and hit a clean 50% volume rise.

9:45 PM – Preshaping: Gently tip the expanded dough out onto your work surface and dust the top lightly with flour. Flip the mass over so the floured side faces directly down. Fold the outer edges cleanly onto itself so that the raw flour coating remains entirely on the outside of the loaf. Round the dough into a loose ball and let it rest on your counter completely uncovered for 30 minutes to relax the gluten network.

10:15 PM – Final Shaping: Dust the top of the resting dough round with flour. Use a dough scraper to flip it over onto your counter so the floured side faces down. Starting at the edge closest to you, pull the two right corners of the dough outward and fold them up into the center. Repeat this exact matching movement across the left side. Roll the dough tightly away from you, shaping it into a perfectly smooth, taut, uniform log. Basket Stabilization & Fridge Retard: Transfer the shaped roll seam-side up into your well-floured proofing basket. Cover with plastic wrap and return the basket to a warm 80°F (27°C) spot for exactly 15 minutes to stabilize. Slide the basket directly into your refrigerator to rise slowly for 14 to 24 hours of cold fermentation retard.

Next Morning – Preheating: Preheat your oven to 500°F (260°C). Place your cast iron pan and lid onto the middle rack to heat up thoroughly for 45 minutes to 1 hour.

Scoring & Loading: Remove the cold marbled dough basket from the fridge. Flip it over gently onto a sheet of parchment paper and score the smooth surface with one clean, long, deep cut using a sharp lame or razor blade.

The Steam Bake: Transfer the dough carefully onto the smoking hot cast iron pan base, drop the heavy lid down tightly to lock in the steam, and bake at 500°F (260°C) with the lid on for exactly 15 minutes.

The Open Bake: Carefully lift the hot lid off to expose the loaf, lower the oven temperature to 450°F (232°C), and continue baking bare for an additional 20 minutes until the crust turns an incredibly deep golden brown. Let cool on a wire rack for 2 full hours before slicing into your marbled cocoa crumb!