Preheat the oven to 375 F.
Cut the squash in half, de-seed, score the flesh several times in a cross-hatch pattern, coat with extra-virgin olive oil, season with salt and pepper, and roast for 45 – 60 minutes, or until very tender. Reserve to cool.
Add the butter to a large stock pot over medium heat.
When the butter has melted, add the onion, season with salt, turn the heat down to medium-low, and begin to sweat.
Add the garlic and continue to sweat until the onion is translucent. Taste and adjust seasoning as necessary.
Scoop the flesh out of the reserved squash, being sure not to include any skin, and add it to the pot. Stir to combine all ingredients.
Wrap all of the ingredients for the bouquet garni, including the cinnamon stick, in cheesecloth and tie off tightly with butcher twine. Add to the soup and grate in the nutmeg.
Stir to combine, add enough chicken stock to just cover the vegetables, season and bring the mixture just to a boil. Turn the heat down to medium-low, cover and simmer for 10-15 minutes.
When the vegetables are soft and the liquid has reduced somewhat, transfer the soup to a blender in batches and puree until smooth.
Return the soup to a clean pot and bring back to a simmer. Add the cream and syrup (if desired) and stir to combine. Taste and adjust seasoning as necessary.
Serve hot in warmed bowls.