In a kettle, combine the chicken with enough salted water to cover it by 2 inches. Bring water to a boil, and simmer the chicken for 20 minutes or until it is tender. Let chicken cool in the broth, separate the meat from the skin and bones, returning the skin and bones to the broth. Cut the meat into strips and reserve. Simmer the broth until it is reduced by half, strain through a fine sieve, discarding the solids. Skim off fat. Boil the stock until it is reduced to about 2 cups. Meanwhile, in a large saucepan, cook the mushrooms in 2 Tbsp butter over mod-low heat, stirring, until they are softened. In a kettle of boiling salted water, cook spaghetti until it is al dente. Drain it well. In a saucepan melt remaining butter over mod-low heat. Add flour and cook the roux, stirring, for 3 minutes. Whisk in the reserved broth, cream and Sherry. Bring the sauce to a boil, whisking, and simmer it for 5 minutes. Season with nutmeg and salt and pepper to taste. Stir half into the mushrooms with the spaghetti and transfer it to a well-buttered 2-1/2-qt. baking dish, making a well in the center. Add the chicken meat to the remaining sauce, combine well. Spoon this into the center of the spaghetti and sprinkle with Parmesan cheese. Bake in the middle of a preheated 350f oven for 25-30 minutes or until pale golden in color. Serve immediately. A 1955 Gourmet Mag. favorite.