Prepare levain (the night before mixing, 9:00 p.m.)
In a small container, mix together the following and keep at 77°F (25°C) for 12 hours.

46g medium protein bread flour
9g sugar
46g water
18g ripe sourdough starter

Mix (9:00 a.m.)
Cut butter it into 1/2″ pats and let warm to room temperature. To the bowl of a stand mixer fitted with the paddle attachment, add:

154g medium-protein bread flour
199g high-protein bread flour
120g pumpkin puree
31g sugar
3g cinnamon
94g water
80g milk
8g salt
119g ripe levain (from step 1)

Mix speed 1 (STIR for KitchenAid) for 1 to 2 minutes until homogenous. Then, mix speed 2 for 8 minutes until dough clumps around the paddle.

Let the dough rest in the mixing bowl for 10 minutes.

Next, add the 64g butter, one pat at a time, while the mixer is running on speed 1 (STIR). Continue this for 5 to 8 minutes until all the butter is added to the dough and it’s glossy and soft.

Finally, add the 80g raisins at the very end of mixing and mix on low just to incorporate.

Transfer your dough to a bulk fermentation container and cover.

Bulk Fermentation (9:30 a.m. to 1:00 p.m.)
Give the dough 3 sets of stretch and folds at 30-minute intervals, where the first set starts 30 minutes after the start of bulk fermentation.

Chill dough (1:00 p.m. to 1:15 p.m.)
Place the bulk fermentation container, uncovered, in the refrigerator for 15 minutes to make shaping easier.

Shape (1:15 p.m.)
Butter or grease the baking pan. Scrape the dough out of the bulk fermentation container to a floured surface and shape the dough as a tube. Place into baking pan and cover.

Proof (1:30 p.m. to 3:30 p.m.)
Proof the dough at 77°F (25°C) for 2 hours.

Bake (3:30 p.m.)
Preheat your oven to 400°F (200°C). For the egg wash, whisk together one egg and a splash of whole milk. When the oven is preheated, brush on the egg wash and bake for 20 minutes. Then, rotate the pan 180° in the oven and reduce the temperature to 375°F (190°C). Bake for an additional 30 minutes until the top is well-colored. Remove the pan from the oven and gently knock the loaf out to a wire rack. Return the loaf (without pan) to the oven to bake for 5 to 10 minutes. The internal temperature should reach around 205°F (96°C). Let the loaf cool for 2 hours on a wire rack before slicing.