10:00 PM – Starter Build: In a small glass jar, add your 10g of starter culture to 40g of water and whisk together cleanly. Stir in 40g of bread 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.

Potato Preparation: Peel and dice your purple sweet potato. Steam or boil the pieces until they are completely fork-tender. Drain thoroughly and mash them using a fine potato ricer or fork until absolutely smooth, ensuring no lumps remain. Let the mash cool completely down to room temperature, cover tightly, and store in the fridge overnight.

8:00 AM – The Enriched Autolyse: In your stand mixer bowl, combine all 110g of whole milk, 120g of your smooth purple sweet potato mash, 35g of sugar, 1 large egg, 80g of your active overnight starter peak, and all 350g of bread flour. Mix everything together with a spoon just until a rough, shaggy purple mass forms. Cover and let rest for 1 full hour to completely hydrate the flour proteins.

9:00 AM – Developing Gluten: Attach your dough hook. Mix the autolysed dough on low speed for 2 to 3 minutes (or use a KitchenAid mixer on speed 3 for 3 to 4 minutes) until well incorporated. Add the 6g of fine sea salt and continue mixing for a couple of minutes until the dough gathers tightly together.

Butter Emulsification: With the mixing machine running, gradually drop in the 40g of soft unsalted butter piece by piece. Once introduced, increase the speed to medium-high and mix continuously for 10 to 15 minutes until the fat is completely incorporated, the dough cleans the sides of the bowl, and it passes a clear windowpane test.

Bulk Proof with Intervals: Cover the container tightly and let it proof for 3 to 4 hours at a warm 76–80°F (24–28°C). During this window, perform 2 gentle rounds of stretches and folds to build structural tension. The dough should look visibly lighter, smooth, and slightly puffy.

1:00 PM – Cold Fermentation Retard: Slide the entire covered proofing container directly into the refrigerator to rise slowly for 7 to 8 hours of cold fermentation retard until evening.

9:00 PM – Sandwich Loaf Shaping: Remove the chilled violet dough from your refrigerator. Tip it onto a lightly floured work surface. Using a rolling pin, roll the chilled dough out cleanly into a long, flat rectangle roughly 1/4-inch thick, ensuring the width matches the length of your loaf pan.

The Overnight Counter Rise: Starting from the edge closest to you, roll the dough up tightly away from you into a tight, uniform cylinder. Pinch the final seam firmly to seal the log closed. Grease your loaf pan with butter or line it with parchment paper, and place the log inside, seam-side down. Cover loosely and let it proof overnight on your counter for 8 to 10 hours at a stable room temperature of 70–72°F (20–22°C) until the next morning. The dough must completely double in volume, rising cleanly past the rim of the pan.

Next Morning – Baking: Preheat your home oven to 375°F (190°C). Brush the towering top crown of your beautifully risen loaf lightly with your prepared egg wash mixture for a glossy finish. Slide the pan onto the middle oven rack and bake for 35 to 40 minutes until the top turns a deep, uniform golden bronze.

Cooling: Remove the pan from the oven, slide the soft loaf out carefully onto a wire cooling rack, and allow it to cool completely down to room temperature before slicing to reveal the vibrant, striking purple interior!