I recently ate a dish that was topped with a foamy bechamel sauce. It had the same creamy taste a traditional bechamel has but was much fluffier and less set, a bit like a mousse. I would like to reproduce this but I am not sure whether a foamer would be enough or I'd need some stabiliser on top. Has anyone got experience with foaming bechamel and/or does someone have a recipe for this sort of thing?
I ended up getting the recipe from the chef himself! It turns out that gelatin makes little sense at the temperatures involved unless you up the quantity in which case the texture gets altered for the worse (I experimented only twice so I can't really be sure that it wouldn't work at all).
The recipe itself calls for a bechamel with a very light roux simmered for a very long time (~3 hours) and stirred occasionally so that the milk doesn't burn. At the end of the process it becomes thick enough to foam in exactly the right texture. Strangely the guy doesn't use any seasoning aside from salt and pepper but I'd think this is so that the particular dish is in balance.
It probably depends on how sturdy you want the foam to be. There are a number of hydrocolloids that you could use. I would start with gelatin. If you are using powdered, start with 1%. Bloom and dissolve into bechamel, bring to a boil. Pour contents into whipper (such as ISI brand), charge with N2O. Dispense as you see fit. If that produces a foam that is too soft, up the percentage of gelatin.