This might be the best use of sweet potato leftovers that I've ever tasted. Delicate, light and balanced. The flavors are outstanding. It's worth making sweet potato cassarole more often, if for nothing else, to freeze and have ready to make this soup! I like to make a fresh stock/broth from the Thanksgiving, or Christmas dinner turkey, and use that, two days later, in this recipe with the cassarole leftovers. Bon Appetit!