Thaw it, remove giblets, rub it with butter, rub inside and out with mix of 1 teaspoon each salt and flour per 5 pounds of turkey. Truss (do not stuff), place it in a large brown grocery bag, fasten with paper clips and roast at 300°, 7 to 10 pounds for 30 minutes per pound, 10 to 15 pounds for 20 minutes per pound, 15 to 18 pounds for 18 minutes per pound or 18 to 20 pounds for 15 minutes per pound. Remove from oven, let stand for 10 minutes. Cut away top of bag, remove turkey, use juices for gravy. To make the dressing, sauté onion, celery and chestnuts in butter. Mix in all other ingredients. Shape into balls with ice cream scoop. Arrange in large casserole. Cover lightly with foil. Bake 1 hour at 350°. Uncover to brown.