10:00 PM: In a small bowl, whisk your 10g of starter culture into 25g of water. Add 50g of bread flour and mix thoroughly. Knead briefly with your hands to form a tight, solid dough ball, then roll it into a firm cylinder.

Place the cylinder into a tall glass jar and fill it completely with room-temperature water 74–76°F (23–24°C) so the dough is completely submerged. Let it sit out overnight for 8 to 10 hours. As it ferments, it will expand, trap gas, and eventually float safely to the top of the water.

8:00 AM: Carefully fish the floating starter ball out of the water jar. The exterior will look wet and slightly dissolved; discard the mushy outer layer and scale out exactly 60g from the firm core center to use in the dough.

In your stand mixer bowl, combine the 60g of extracted stiff starter, 125g of milk, 125g of water, 3 egg yolks, 340g of bread flour, and 90g of sugar (add the optional 0.5g of dry yeast here if using). Mix briefly until a shaggy mass builds, cover, and let autolyse for 30 minutes.

8:30 AM: Lock your mixer's dough hook in place. Run it on the low speed of your machine for 2 to 3 minutes (or if using a KitchenAid mixer, run it on speed 3 for 3 to 4 minutes) until uniform.

Sprinkle in the 7g of salt and continue mixing for 2 minutes until a clean ball takes shape.

Increase your mixer speed to medium-high and begin introducing the 55g of soft butter a tablespoon at a time. Knead intensely for 10 to 15 minutes until the dough builds enough gluten strength to gather up smoothly away from the bowl walls. Note: If the rich dough remains unmanageably sticky after 12 minutes, sprinkle in a small 10g to 20g adjustment of flour to help it clear the bowl.

9:00 AM: Cover the bowl and let proof for 3 to 4 hours at a warm ambient temperature of 76–80°F (24–28°C). Perform 2 separate rounds of structural stretch-and-folds during this window; the dough will become light and slightly puffy.

12:00 PM: Transfer the covered container directly into the refrigerator for a long cold fermentation rest until the next morning.

7:00 AM: Lightly dust your workspace with flour and tip the cold dough out. Use a rolling pin to flatten and stretch it into a clean, wide rectangle measuring exactly 8x15 inches (20x38 cm).

Using a pizza wheel or sharp knife, cut the rectangle lengthwise into 6 equal, long strips. Generously brush your 50g of melted butter over the entire surface of each strip.

Roll each buttered strip up lengthwise into a tight, compact coil, cleanly tucking the loose tail end underneath the base to secure it.

Using the flat palm of your hand, press firmly straight down on top of each coiled roll to flatten it slightly, then arrange them onto a baking sheet lined with parchment paper. Cover loosely and let proof on the counter for 2 to 4 hours until they look visibly wider and puffier.

Preheat your oven to 375°F (190°C). Slide the tray inside and bake at 375°F (190°C) for exactly 10 minutes to lock in the oven spring.

Lower the oven temperature down to 350°F (175°C) and continue baking for an additional 10 to 15 minutes until the tops turn a uniform light golden brown. Remove from the oven and let them cool down completely. Once cool, dust the tops generously with your 3 tablespoons of powdered sugar before serving.