This was delicious and a big hit with everyone, especially my noodle-loving daughter. She was a bit dubious, until I explained that this was like macaroni and cheese, but with chicken and peas. Peas! Mushrooms are not a favorite (except with me), so I used peas instead. Also, I have not scored a turkey yet, despite scouting the Chicago markets, so I used leftover fried chicken-- that was good. My husband and I enjoyed it with a bit of hot sauce on top. To make up for the lack of mushroom umami, I added a bit of Worcestershire sauce.
This made a huge amount and next time I would make two smaller casseroles and freeze one. In fact, I'm thinking about doing that for my cousin, who is due with twins in 2 weeks. So, should I freeze it before baking or after? Also, what should I tell them for baking instructions? Your advice would be most welcome.