1) Coat the Dutch oven with cooking spray and heat it over medium heat.
2) Put the onion and sautÃ© until tender.
3) Add the squash and next four ingredients.
4) Reduce the heat and simmer for 30 minutes.
5) Remove from heat and pour the mixture into the container of an electric blender and process them until smooth.
6) Keep the mixture into Dutch oven and stir in milk.
7) Cook them until the mixture is heated completely.
8) Serve the soup hot with any of your favorite side dish.