Melt the butter in a medium soup pot over medium -low heat until melted. Add the onions and allow them to cook for about 5 minutes until they are translucent. Add the garlic, spices and cook for about one minute. Add the chicken broth, bring to a boil, reduce the heat and allow the mixture to simmer for about 20 minutes.
Stir in the pumpkin and the half and half and continue cooking for about another 5 minutes.
Remove from heat. Using an emersion blender puree the soup until smooth. If you choose to use a regular blender, allow the soup to cool slightly then fill the blender no more than a third of the way before turning it on.
Stir in the Sherry wine and maple syrup and adjust the seasonings to taste.