Preheat oven to 350 degrees.

Cut the squashes in half lengthwise. Scoop out the seeds and discard.

Place the squash halves cut side up in a roasting pan. Divide the butter and maple syrup evenly amongst the squash cavities. Arrange the carrot and onions slices around the squash. Pour 2 cups of stock in the pan and cover tightly with foil. Bake for 2 hours.

Remove the pan from the oven and allow the vegetables to cool slightly or enough that you can handle them. Scoop the squash pulp from the skins and transfer to a large soup pot. Add the carrots, onions and cooking liquid from the pan.

Add the remaining 8 cups of chicken stock to the pot with cayenne and salt to taste (I usually add 1 Tablespoon when I use unsalted stock.) Stir well and bring to a boil. Lower heat and simmer, uncovered for 10 minutes.

Puree the soup until smooth in the pot with an immersion blender or in batches in a blender. Taste for seasonings.