Question: I guess it's technically a Mornay, it has Parmesan and Fontina. I've got about 1 1/2 cups in my fridge. Refrigerated it's solid enough to hold a knife vertically, when it was warm it was just barely pourable and self spreading. It's a darn good sauce, I'd hate to waste it, but after all my adventures lately making an 'ultimate' lasagna, I won't end up using it for pasta. I'd like to put it to use in an entirely different way, preferably with a totally different flavor profile.

Any ideas?

Bonus points if it would make a nice lunch for the day after the extreme lasagna dinner.

Answer: 
Crouque-Monsier or the similar "Hot Brown" sandwich is perfect for my needs. That will use up the sauce in a completely different way. It will also make a great lunch. Thanks SAJ14SAJ for the tip.
If you want something kind of healthy, you can always mix it with steamed spinach and it can't be more delicious!!! Oh, with brocoli works pretty well too ;-)