Activate the yeast: Whisk together the active-dry yeast, milk and maple syrup in the bowl of your stand mixer. Cover with plastic wrap and let the yeast bloom until foamy and fragrant, about 15 minutes.
7 g active-dry yeast, 113 g milk, 28 g maple syrup
Make the dough: Add the egg, pumpkin puree and sourdough discard into the yeast mixture. Whisk the ingredients in until well combined.
120 g pumpkin puree, 1 egg, 113 g sourdough discard
Add the flours and salt into the bowl of your stand mixer and mix on low speed using a dough hook until a shaggy dough forms.
300 g all-purpose flour, 60 g whole wheat flour, 9 g salt
Increase the speed to medium low and add the butter into the dough one tablespoon at a time. The dough should look gradually less greasy as the butter is absorbed.
56 g unsalted butter
Cover the bowl with plastic wrap and let the dough rest for 15 minutes. This gives the flour time to fully hydrate and allows the dough to gain strength without overmixing, which can cause it to become too warm and impede gluten development.
After the rest period, knead the dough using the dough hook at medium speed until it looks completely smooth and pliable, about 3 to 5 minutes. The dough should cling to the hook and release from the sides of the bowl.
Proof the dough: Turn the dough out on a clean work surface and lightly knead it a few times. Round the dough into a tight ball and transfer it to a lightly-greased bowl. Cover the bowl with plastic wrap and let the dough rise untouched until doubled in volume, about 45 minutes to 1 hour. (See note)
Prep: Brush a 8 by 5 inch loaf pan with butter, then line it with a piece of parchment paper (optional).
Shape the loaf: Turn the dough out on a lightly floured surface and divide the dough into 6 even portions. Round each portion into a tight ball. Nestle each ball into your prepared loaf pan. (See note)
Final proof: Cover the pan with plastic wrap and let the dough proof until it fills the pan, about 30 to 45 mins.
Preheat the oven: When the dough is almost fully proofed, preheat the oven to 350 F.
Bake the loaf: Brush the top of the dough with egg wash. Bake for 40 to 45 minutes or until golden brown and the center of the loaf measures 190 F when probed with an instant-read thermometer.
1 egg
Enjoy: Transfer the loaf immediately to a wire rack and let it cool completely before slicing.
Store: Store any leftover slices in an airtight container for up to 1 week at room temperature or freeze the slices for up to 1 month.