To roast the squash, preheat the oven to 400F. Line a baking sheet with parchment paper. Holding the squash parallel to you, cut off the stem of the squash, halve and slice the squash into 2-3 large sections. Scoop out any seeds and pulp. Prick the skin (each section about 4-5 times) with a fork or knife.
Place the squash pieces flesh side up on the prepared baking sheet. Drizzle the squash with oil and sprinkle lightly with salt. Turn over the squash pieces so the skin is facing up, then place the baking sheet in the oven for roasting. Bake for 35 minutes or until the flesh is soft and easily pierce-able with a fork or knife. Let cool completely, then scoop out the flesh with a spoon. Mash with a fork or the back of the spoon.
In a large vessel, combine the squash, coconut milk, starter, and sugar. Add the whole wheat flour and bread flour. Squeeze with your hand to combine thoroughly, then cover and let autolyze for 1 hour.
After autolyze, sprinkle the salt, cinnamon, and nutmeg over the dough. Squeeze and fold to combine completely into the dough, being careful not to break the dough as you combine. Allow to rise at room temperature overnight (8-10 hours).
In the morning, mix the cinnamon filling ingredients thoroughly in a small bowl. Thoroughly grease a 10-inch cake tin or cast-iron skillet with coconut oil or vegan butter.
Flour a surface and roll out the dough into a 11x14-inch rectangle. Evenly spread the filling over the dough with an offset spatula. With the wider side facing you, roll up the dough, but not too tightly so the buns have room to rise.
Use a sharp serrated knife to slice the dough into 8 even parts. Place the buns face up in the pan (one in the center, and seven in the surrounding).
Cover and let proof for 2 hours. 20 minutes from the end of the proof, preheat the oven to 375F.
When the proof is finished, the buns should have filled the space and no bottom of the pan should show!
Uncover and bake for 40-45 minutes, or until the internal temperature reads 200F. Serve warm and enjoy! Let me know what you think below in the comments or on Instagram @higheralchemybaking!