You might also try a thinner initial liquid to account for reduction and splitting. If the sauce gets too reduced in the casserole it can separate out that way. If anyones every over-reduced an alfredo or other cream sauce you might know what I mean.
Flour should give you some protection against splitting but it won't last forever. You also might try adding a bit of cream to the mix as well...it has natural emulsifying agents that may work with the cheese and other fats in the sauce to help bind it.
Flour should give you some protection against splitting but it won't last forever. You also might try adding a bit of cream to the mix as well...it has natural emulsifying agents that may work with the cheese and other fats in the sauce to help bind it.
