Melt butter in a large saucepan. Add the shallots, onion, and celery; cook over low heat about 6 minutes (keep stirring). Add chicken stock, nutmeg, and sweet potatoes. Bring mixture to a boil, lower the heat, and simmer for about 30 minutes. When the potatoes seem tender, put the mixture into a food processor or blender and mix until smooth. Put mixture into a saucepan and add the half and half and sherry. Stir to mix and smooth out. Season with pepper and continue to heat but don't bring to a full boil. Place walnuts in a small dish and have each diner sprinkle the chopped walnuts in the filled soup bowl. Serves about 6 people. From the kitchen of Judi M. Phelps. jphelps@slip.net or jphelps@best.com ----