If you don’t use the béchamel immediately, pour it into a bowl and let it cool, then cover it with cling film so that a skin does not form on the surface. Once cold, the béchamel can be stored in the refrigerator, closed in an airtight container, for a maximum of 2-3 days.
To make it smooth and creamy again, just work it with the whisk of an electric mixer; if necessary, you can add a little milk to make it more fluid when being whipped.
The béchamel can be frozen for about 1 month.