Preheat pie shell 10 minutes at 400 degrees. Wash spinach and mushrooms twice. Cook mushrooms in a skillet with butter, salt, pepper and garlic to taste. Drai n well. Cook spinach in boiling salted water. Drain and cool. Extract all water . In a large bowl, combine spinach, mushrooms, and sour cream. Recheck seasonin g. Mix well together. Pour into pie shell. Sprinkle cheese on top making a full covering. Bake at 350 to 200ºC or 30 minutes. Cool before serving so mi xture will set better. Can be kept in refrigerator for several days. Will not f reeze. Recipe from "One Million Recipes CD" busted by Judy R.