Heat olive oil in large saucepan over medium heat until hot. Add onion, celery, carrot and cinnamon stick; sauté until soft but not brown, about 10 minutes.
Season with salt and pepper. Add broth and coriander; bring to a boil. Simmer for several minutes.
Stir in reserved squash until smooth; simmer gently to let flavors meld, about 10 minutes.
Discard cinnamon stick.
Pureé soup using an immersion blender or in a blender until smooth. (The soup can be made ahead to this point, cooled, covered, and refrigerated for several days or frozen for about 1 month. It will thicken as it cools and may need thinning with broth or water when reheating.)
Return soup to pan and reheat gently. Add half-and-half. Adjust seasoning with salt and pepper.