Melt the butter in a saucepan over low heat. Add the flour to the butter and mix thoroughly to avoid lumps.
Add cream, salt and spices, continue mixing for 3-4 minutes.
Pour in milk, but do not bring to a boil, stir until smooth. Add dried herbs or fresh chopped greens if desired.
Pour the finished sauce into a glass jar and close the lid. Let it cool at room temperature, then put it in the refrigerator for storage. By storing it in a closed jar, you will maintain the hermetic seal and avoid foreign odors.