1. Place the whole chicken in a kettle and add water barely to cover. Add the celery stalk, parsley and a little salt. Bring to a boil, cover and simmer until the chicken is tender, two to three hours. Remove the chicken to a warm platter and keep hot. Strain the stock and reserve one cup.
2. In a saucepan melt the butter, add the flour and stir with a wire whisk until blended. Meanwhile, bring the reserved stock and the cream to a boil and add all at once to the butter-flour mixture, stirring vigorously with the whisk until the sauce is thickened and smooth. Season with the nutmeg, one-half tea spoon salt and the pepper.
3. Preheat oven to hot (400° F.).
4. Cook the macaroni in two quarts boiling salted water until tender, about ten minutes. Drain and mix with half the sauce. Stuff the chicken with the mixture, close the opening and truss. Place, breast side up, in a buttered baking dish. Pour the remaining sauce over the top and sprinkle with grated cheese. Bake until the cheese is browned, about ten minutes.