My exact comment too. We made two batches and loved it, except that we went a little
crazy with extra cheese and it was too soupy. But taste-wise it was great.
We made up a batch for Bachelor Bob and he was thrilled to get a hot casserole breakfast on Christmas morning.
We followed Dawn_MO advice and just used what we liked. Croissants, sauteed onion, mushrooms, celery (use the rest for stuffing), diced ham, montery jack and cheddar, then the top croissants. The tops ended up nice and crispy.
We baked the second casserole a bit longer. Definitely a keeper.