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 10 to 12 hours until the starter reaches its peak and triples or more in volume.

Purple Potato Prep: Boil your purple sweet potatoes until fork-tender. Drain thoroughly, peel, and mash them with a fork or potato ricer until completely smooth and free of lumps. Let the mash cool completely down to room temperature overnight.

7:00 AM – The Core Autolyse: In your stand mixer bowl, combine the 270g of high-gluten flour, 30g of whole wheat flour, and 207g of 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.

8:00 AM – 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.

8:30 AM – Salt Incorporation & Division: Add your 6g of salt directly to the bowl. Mix on low speed for 1 to 2 minutes (or on a KitchenAid on speed 3 for 2 to 3 minutes) until well incorporated. Using a digital scale, divide the dough mass into 2 precisely equal pieces.

Blending the Inclusions: * Place Dough piece #1 into a bowl and mix in the extra 9g of water to increase its hydration. Place Dough piece #2 into a separate bowl and incorporate the 100g of cold mashed purple sweet potato. Use your hands or a mixer to fully combine each batch. Both pieces will feel sticky but should pull together into cohesive units. Cover both bowls and let rest for 30 minutes at 74–78°F (23–26°C).

9:00 AM – The Grand Lamination: Wet your hands and spray your clean work surface lightly with water. Take Dough #1 (White) and stretch it out as thin as possible across the table without tearing the matrix. Repeat the exact same thin stretching action with Dough #2 (Purple) on another surface (or set the white sheet aside). Place the purple dough sheet directly on top of the white sheet. Fold the layered sheets neatly over on top of each other into a neat package to trap the colors, transfer to a bulk container, and let rest for 30 minutes.

9:30 AM – 1st Stretch & Fold: Wet your hands slightly. Lift one side of the layered dough up cleanly from the container edge and fold it 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.

10:15 AM – 2nd Stretch & Fold: Execute your second structured round of quadrant folds to continue organizing the expanding, colorful gluten network. Cover and let rest for 45 minutes.

11:00 AM – 3rd Stretch & Fold: Execute the third and final stretch-and-fold round. Cover and let the dough proof completely untouched for 40 minutes at a warm 76–80°F (24–27°C). The dough should look visibly lighter, show distinct surface bubbles, and hit a clean 40% to 50% volume rise.

11:40 AM – 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.

12:10 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 roll.

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) environment 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 purple 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 to reveal the vibrant colors inside.

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 to reveal your gorgeous purple swirl crumb!