Prepare casserole in foil-lined baking dish, making sure there is enough foil extending over edges of dish to cover and seal. Freeze casserole until firm. Remove from dish; wrap tightly with foil. Place foil-wrapped casserole in freezer-weight resealable plastic bag. Label and date. When ready to thaw, unwrap frozen casserole and return to original baking dish. Thaw overnight in refrigerator, then bake as directed just before serving.