Cooking Question

Okay... there's one area of cooking that's COMPLETELY new to me.... and that's make-ahead cooking.  I love my freezer and I freeze a lot of things other people (read Frog Prince) think are strange, like cheese and butter. 

But, despite my relationship with my freezer, I am new to the make a whole meal, stick it in the freezer and just reheat thing. 

So, I'm going to attempt to make something ahead!  Here's where I need your help. 

I'd like to make this delicious creamy spinach dish ahead of time.... but, I'm leery of freezing a cream sauce. 

Have any of you frozen a "cream sauce" dish?  Or, should I prepare the pasta and spinach/mushroom base, and make the sauce fresh before I cook it? 

And, do I need to "dethaw" the dish, or can I just stick it in the oven to cook (albeit a little longer than normal)? 

Any advice you can offer this cook would greatly appreciate!