Remove the required portion from the freezer. Thaw it for 12 hours in the fridge and reheat it in the microwave or on the stovetop. While reheating if the sauce turns too thick, add one or two tablespoons of milk to adjust the consistency of the sauce. Do not thin down the sauce too much. You want the spinach cream sauce to be thick enough. You can directly reheat frozen creamed spinach in a microwave-safe bowl. Reheat it for 60 seconds interval and stir often. Add a splash of milk if needed if the sauce turns too thick while reheating.