In a microwave: put the frozen spinach in a microwave-safe dish. Cook covered for 8-10 minutes (cooking mode). Stir from time to time. After cooking, you can add some butter or cream. Season and serve, In a frying pan: put some butter in a frying pan, heat and add the spinach. Add salt, pepper and nutmeg. Once the excess moisture is absorbed, add a knob of butter.