would freeze!!! I made some a while back and had extra so threw in a plastic bag and froze it.
I've been reading up on Escolar (have some in the freezer) and a number of readings suggested it needs a sauce served with it. So, I heated the frozen bechamel in a bain marie and added a little cheddar, worcestershire and stone ground mustard. Thinned with white wine. It worked!! Not the least grainy, it was just a smooth, very tasty sauce for the Escolar.
The Escolar, by the way, I had never tasted nor cooked before - it's great!! Seems to be a fish you either love or dislike, not much in between.
I'll never throw out extra bechamel again!!