Cut chicken into 6 or 8 pieces; remove and discard skin. Place chicken and next 7 ingredients in a large (6-quart) soup pot, stirring until well blended. Bring to a boil; reduce heat, and simmer, covered, 30 to 40 minutes or until chicken is tender.
Remove pot from heat; remove chicken pieces from soup pot, reserving broth. Let chicken stand until cool enough to handle. Remove chicken from bones, and cut into bite-size pieces. Stir chicken and sherry, if desired, into broth mixture. Bring to a boil, reduce heat, and simmer.
Combine flour and next 3 ingredients in a small bowl. Cut in butter with a pastry blender or fork until mixture resembles coarse meal. Add buttermilk, stirring just until mixture comes together.
Drop tablespoons of dumpling batter into hot broth. Cover and simmer 10 to 15 minutes or until dumplings are cooked through.
*Substitute 4 bone-in chicken breasts for the whole chicken, cut into pieces, if desired.