Blend butter and flour in the top of a double boiler over simmering water. Stir in eggs and lemon rind. Stir in cream and milk alternately, a little at a time; continue stirring until smooth and slightly thickened. Add crab meat and let simmer for 5 minutes. Stir in Worcestershire sauce and sherry, then season to taste with salt and pepper. Serve in heated soup bowls with a sprinkling of parsley. Serves 10.