The procedure:
Mix together the ingredients for the sponge in a large bowl, whipping it if you can to aerate the mixture. Set it aside while you prepare the flour mixture.

Mix together the ingredients for the flour mixture, whisking it together to make sure the ingredients are incorporated fully and spoon over the sponge. Cover the bowl with plastic wrap and let it rest for one to four hours; or, until you see the sponge bubbling up through the flour mixture. Since it’s wintertime where I live, I waited about four hours before proceeding with the rest of the recipe.

After you can observe the sponge bubbling up through the flour mixture, add the oil and mix the dough together, either with a stand mixer or by hand. I did this by hand as the amount of dough was so small. Mix until the dough is smooth and homogenous looking; as the hydration of the dough is higher than your standard sandwich loaf, it will feel tacky and sticky. This is fine. Continue kneading the dough until you achieve good gluten structure and the dough passes the windowpane test. This took me about ten minutes by hand.

Place the dough in a lightly-oiled bowl and let it rise until doubled, about 1 1/2 to 2 hours. After this first rise, take the dough out and degas it, you can do a couple of stretch-and-folds to give it better structure, then place it back into the bowl and let it rise again for 45 minutes.

After 45 minutes have elapsed, take the dough and degas it gently and shape it (you can do a small boule or shape it sandwich style if planning to bake in a loaf pan). Place the dough in your chosen baking receptacle and let it rise a third time until doubled, about 1 1/2 to 2 hours. Half an hour before you are ready to bake, preheat the oven to 400 F.

When ready to bake, place the loaf into the oven, steam (if not baking in a pullman tin) and lower the temperature to 375 F and bake for 25 minutes. Check to see if the bread is done by inserting a thermometer into the center of the loaf and making sure it reads at least 190 F. Invert the bread onto a cooling rack and let it cool for at least 4 hours before slicing to enjoy.

Making the filling:

Steam kuri squash until flesh yields easily when poked with a fork. Let cool slightly, then scoop out the flesh and roughly mash (no need to make it very smooth, you’ll be working the flesh during the sweetening phase).

In a medium saucepan, combine the kuri squash flesh, raw sugar and salt, and over medium heat, stir until sugar is dissolved. Keep cooking the sweetened squash puree (this process helps to dry out the paste, you don’t want soupy squash as a filling for the buns) until it stops looking shiny and pulls away from the sides of the pan. Turn off the heat and let cool completely.

For the bao dough:

Whisk together the whole wheat flour, all purpose flour, yeast, and salt. Add the agave nectar and vegetable oil and water, stir to combine until you get a rough dough.

Turn dough out onto counter and knead until you have a smooth, supple dough. I didn’t use my stand mixer as the amount of dough was small (and sometimes you just want to experience the pleasure of working with bread dough!). Knead until it passes the windowpane test, with a 5 minute rest halfway to allow the dough hydrate and the gluten to relax slightly.

Place in a medium, oiled bowl, cover with plastic wrap and proof until doubled in size. In my cold house, it took about 1.5 hours.

Preheat the oven to 375 F.

Once the dough has doubled, turn it out onto the counter and give it a few kneading strokes, and let it rest for 5 minutes for the gluten to relax. Divide the dough into 5 pieces.

Divide the filling into 5 mounds in preparation for stuffing the bao.

Flatten each piece, and using a small rolling pin, roll out into a 5″ diameter circle, taking care to make the edges thinner than the center (so that when you gather the dough around the filling you don’t end up with a super thick bottom and a super thin top). Place 1 mound of sweetened squash filling in the center and draw up the edges of the dough around the filling; pinching the dough at the top to seal.

Place seam side down on baking sheet, and cover with a kitchen towel while you complete the rest of the bao. After filling all 5 bao, let proof for 20 minutes.

I mixed together a simple slurry of almond milk, cornstarch and a pinch of sugar for a matte-style wash. If you desire a shiny-type of wash, simply beat one egg with some water. Brush the tops of the proofed bao with your wash of choice and sprinkle with some sesame seeds for garnish.

Bake bao for 25 minutes (if they start to brown too fast, you can tent with a piece of foil to avoid overbrowning).

Let cool completely on racks for at least 8 hours (this allows the dough to finish cooking completely, if you were to eat them right away, you might find the dough directly underneath the filling to be slightly raw. After 8 hours, the dough will have finished cooking and the flavor will be better. This is generally true of most breads.)

Enjoy! My favorite way to eat these is to reheat them for 20 seconds in the microwave, then pop into the toaster for a little bit to get them slightly toasty on the outside. The outside becomes slightly crispy and the inside bread stays light and fluffy. Delicious!

Cooking Notes:

• I know that squash comes in various shapes and sizes, and my kuri squash, after halving and deseeded, was about 500g. After steaming and making it into sweetened puree, the yield was about 250g. Basically, you’re aiming for about 50g of sweetened filling per bao. If your squash is abnormally large or small, you can scale up/down the dough component. Or you can just eat the extra filling as is, it’s delicious that way too!
• Any type of squash, pumpkin, sweet potato/yam or even beans can be sweetened in this way; it’s really a universal technique that you can apply to many vegetables/legumes to make sweetened paste for bun/bao fillings, dumplings, etc.
• This dough is pretty versatile, besides using it as a baked bao dough, this dough makes steamed bao quite nicely too. Give it a try!

The Procedure:

On the night prior to baking, in a large bowl, mix together the ingredients for the poolish. Cover with plastic wrap and let it sit overnight.

The next morning, combine 2 cups (240g) of the flour, the yeast, sugar, and the onion soup mix. Mix in all of the previous night’s poolish, milk, egg, and butter, adding more flour if required to make a dough that is smooth, moist, tacky, but not sticky. This is an enriched straight-ish dough, so we’re not looking for a high-hydration artisan type of dough here.

Knead the dough (either by hand or by stand mixer) until proper gluten development is achieved (I always test using the windowpane method.) Place the dough into a greased bowl, mist lightly with oil, and cover with plastic wrap. Allow the dough to rise until doubled in size, approximately 90 minutes. This is the first fermentation.

After the first fermentation, remove the dough from the bowl and shape it into a braid (the recipe on The Fresh Loaf has a good illustrated tutorial), or whatever shape you like. Cover the loaf with a towel or plastic wrap and allow it to double in size again, approximately 45 minutes. While you are waiting for the second fermentation, preheat the oven (and baking stone, if you have one) to 450F (230C).

Just before baking, mix together the ingredients for the egg wash and brush the top of the loaf lightly with the wash. Place the loaf into the hot oven, reducing the temperature to 375F (190C) after 5 minutes. Bake for another 30 minutes, rotating the loaf halfway through the baking time. If the bread starts to look to dark due to the glaze, tent the loaf with a piece of aluminum foil to prevent further browning.

The loaf is done when dark-golden brown and the inside temperature registers at least 190F (85C). Please please please always test the inside temperature of your breads as the last thing you want to do is cut open a beautiful-looking loaf to find a gooey, underbaked mass inside! Let it rest for at least an hour (the bread continues to cook as it’s cooling!) before slicing.