Grease a large baking dish. Heat butter in a large skillet over medium-high heat; add mushrooms and celery. Cook until celery is tender about 5 minutes.
Add sherry and pimientos to skillet; stir. Sprinkle flour over vegetables. Stir Well. Add milk to skillet and cook, stirring continually, until thickened, about 3 minutes. Stir in turkey and salt. Place hot spaghetti in prepared baking dish. Top with turkey mixture; sprinkle with Parmesan. Bake until sauce is bubbly and cheese is browned about 25 minutes.