10:00 PM: In a small glass jar, dissolve your 7g of starter culture into 35g of water. Stir in the 35g of bread flour until smooth. Cover loosely and let it ferment at room temperature 74–78°F (23–26°C) for 8 to 10 hours until it reaches its peak and at least triples in volume.

Make the Tangzhong: In a small saucepan, whisk together the 20g of bread flour and 100g of milk until no lumps remain. Cook over medium heat, stirring constantly, until the heat gelatinizes the starches into a thick, translucent paste. Cover and let it cool down completely to room temperature before adding to your dough.

8:00 AM: In your stand mixer bowl, combine the 200g of milk, 70g of mature sourdough starter, all of your cooled Tangzhong paste, 65g of sugar, 12g of dry milk powder, 1 egg yolk, and 30g of sweetened condensed milk (add the optional 1g of dry yeast here if using). Whisk thoroughly by hand until unified, then dump the 370g of bread flour on top.

Mix the dough on low speed for 2 to 3 minutes (or if using a KitchenAid mixer, run it on speed 3 for 3 to 4 minutes) until a shaggy mass forms and no dry pockets remain. Sprinkle in the 8g of salt and mix for a couple more minutes until a loose ball begins to take shape.

Turn your machine up to medium-high speed and begin dropping in the 40g of soft butter a tablespoon at a time. Knead intensely for 10 to 15 minutes. The dough will look very wet and sticky initially, but keep running the mixer—it will fully incorporate the fat, develop a glossy sheet, and pull completely away from the bowl walls.

Cover the bowl and let bulk ferment for 3 to 4 hours at a warm 76–80°F (24–28°C). Perform 2 separate rounds of structural stretch-and-folds during this window; the dough should look noticeably light and puffy.

12:00 PM: Transfer the covered dough container directly into the refrigerator for a long cold fermentation rest lasting 8 to 9 hours to cool and stabilize the fats for clean shaping.

9:00 PM: Remove the cold dough from the fridge. Using a bench scraper and kitchen scale, divide the firm mass cleanly into 16 equal pieces (weighing roughly 55g each). Round each portion into a tight ball, cover, and let rest for 5 to 7 minutes to relax.

Pan Assembly: Using a rolling pin, flatten each ball out into a thin strip, then roll the strip up tightly lengthwise into a compact roll measuring roughly 5 inches long. Arrange the 16 rolls side-by-side tightly into a greased standard 9x5 inch loaf pan. Cover loosely and let proof on your counter overnight for 8 to 9 hours at 70–72°F (20–22°C) until they double in size.

7:00 AM: Preheat your oven to 375°F (190°C).

Slide the puffed pan loaf into the oven and bake at 375°F (190°C) for exactly 15 minutes to secure a tall, proud oven spring.

Lower the oven temperature down to 350°F (175°C) and continue baking for an additional 12 to 14 minutes until the top turns a uniform, rich golden brown.

The Glaze: While the bread finishes baking, whisk together 1 tablespoon of honey and 1 tablespoon of water in a small cup until completely liquefied.

Remove the hot Pai Bao from the oven. Using a pastry brush, immediately spread your honey glaze generously across the piping hot top crust. Let the loaf cool completely before pulling the signature rolls apart to shred and serve.