How can I safely reheat a frozen casserole to ensure it is thoroughly heated and ready to serve?

To safely reheat a frozen casserole, first thaw it in the refrigerator overnight. Then, preheat your oven to 350F and cover the casserole with foil. Bake for about 30-45 minutes or until it reaches an internal temperature of 165F. Let it rest for a few minutes before serving to ensure it is thoroughly heated.