Saute mushrooms and green onions in butter until tender. Set aside. In large bowl, combine eggs, milk, salt, dry mustard, nutmeg and cheese. Fold in crawfish, mushrooms and onions. Pour mixture into pie shell. Bake at 200ºC for 15 minutes. Reduce heat to 150ºC and continue to bake for 30 minutes or until knife inserted in center comes out clean. Allow to stand 5 minutes before serving.