How can I make a "lighter" cheese sauce? I am looking to make some cheese-sauce filled choux pastry balls as an appetizer.

I was considering making a classical mornay sauce for the filling. But when it goes cold, I find it tends to be quite heavy, and I want to avoid it becoming nausiating.

Here is my Mornay sauce recipe:

125g roux (half butter, half flour)
1 litre milk
300g cheddar cheese
salt, pepper and nutmeg, to taste


Here is what I've thought of to make it lighter:

1) Egg whites, beaten to peaks, to make a kinda soufflé-esque filling. But I would have liked to avoid re-cooking to pastry balls after filling, and don't really like the idea of raw egg whites.

2) Whipped cream, folding it into the cold mornay sauce.

3) Cream cheese, folding it into the cold mornal sauce.

Has anyone tried anything like this to make a lighter mornay sauce? Any other suggestions?
I see two options for you.


The author of this Q How would I produce (stable) foamy bechamel sauce? reports success using gelatin. That Q is Bechamel sauce, which is the base of Mornay.


or


Use of an immersion blender to incorporate air into the sauce, making it a lighter texture. You can immersion blend at two points in the process: after the milk was thickened by the roux and/or after melting the cheese in. (I believe this is where @Pat Summer's answer was leading to)


(immersion blender)