Tracy got this recipe from the epicurious site. She's made it several times and it's awesome. The whipping cream isn't really necessary--the soup is rich enough without the cream--nor is the cider-sour cream necessary, because the soup is already quite sweet.
BUTTERNUT SQUASH SOUP WITH CIDER CREAM Apples and apple cider lend a pleasant sweetness to this beautiful soup. 5 tablespoons butter 2 1/2 pounds butternut squash, peeled, seeded, cut into 1/2-inch pieces (about 6 cups) 2 cups chopped leeks (white and pale green parts only) 1/2 cup chopped peeled carrot 1/2 cup chopped celery 2 small Granny Smith apples, peeled, cored, chopped 1 1/2 teaspoons dried thyme 1/2 teaspoon crumbled dried sage leaves 5 cups chicken stock or canned low-salt chicken broth 1 1/2 cups apple cider 2/3 cup sour cream 1/2 cup whipping cream Chopped fresh chives Melt butter in heavy large saucepan over medium-high heat. Add squash, leeks, carrot and celery; sauté until slightly softened, about 15 minutes. Mix in apples, thyme and sage. Add stock and 1 cup cider and bring to boil. Reduce heat to medium-low. Cover and simmer until apples are tender, stirring occasionally, about 30 minutes. Cool slightly. Working in batches, purée soup in blender. Return soup to pan. Boil remaining 1/2 cup cider in heavy small saucepan until reduced to 1/4 cup, about 5 minutes. Cool. Place sour cream in small bowl. Whisk in reduced cider. (Soup and cider cream can be made 1 day ahead. Cover separately and refrigerate.) Bring soup to simmer. Mix in whipping cream. Ladle soup into bowls. Drizzle with cider cream. Top with chives. Serves 10. Bon Appétit November 1998