In a saucepan over low heat, melt butter. Add soups and mushrooms. Stir until well blended. Remove from heat; add pimiento, chicken, spaghetti, and sour cream. Turn mixture into a greased 13x9x2-inch baking pan. Sprinkle with Parmesan cheese. Bake, uncovered, at 350° for 30 to 35 minutes. Chicken and spaghetti recipe serves 4 to 6.