Peel the squash, trim both ends, and cut it in half lengthwise. Scoop out and discard the seeds. Cut the squash into medium-size chunks. Peel the carrots and chop them roughly. Roughly chop the celery and onions.
Melt the butter in a large stockpot set over medium heat, and add the squash, carrots, celery, onions, and garlic. Cook until softened but not browned, and then add the thyme and cinnamon. Add the stock, bring to a boil, reduce to a simmer, and cook until the squash is soft, 25 to 30 minutes.
Fish out and discard the thyme stems and cinnamon stick. Using a food processor or hand blender, puree the soup (in batches, if using a food processor) until it's smooth. Stir in the cream and season to taste with salt and pepper.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.