I'd say the cream of mushroom soup is trying to emulate a white sauce - a true white sauce would be better IMHO.
Here's how I make mine:
I buy a rotisserie chicken - they are cheap and have a great flavor (ok, it's not homemade
pack of 12 or so flour tortillas
20 ounces or so of Monterey Jack cheese
1 onion chopped (somewhere around 1 cup
1/4 cup butter
1/4 cup flour
2 cups chicken broth (or the broth if you boiled your own and it's flavorful enough. You can always add some chicken base for flavor)
1 cup sour cream
1 8 oz. block cream cheese
1 can green chilies
Red Enchilada sauce - I do buy this though - sorry
Chop up or "pull" chicken - I prefer "pulled" if possible.
Make a roux with your flour and butter (i.e., for those that don't know - melt butter, add flour, stir on medium heat for about 3 minutes to remove flour taste then proceed with recipe).
While whisking, slowly stir in chicken broth to prevent clumping. Once all the broth is in stir in sour cream, cream cheese (cut this in chunks so it melts faster). DO NOT BOIL THIS MIXTURE! Add green chilies.
I heat some red enchilada sauce, dip my tortillas in to coat and soften. Place some chicken, cheese, and onions on the side closest to you and roll up, folding in the sides after a roll or two. Do not over stuff. Place seam side down in casserole dish. Pour on white sauce and if you want you can even drizzle some of the red or green (or both) enchilada sauce of it too - it's good that way.
You can also add some black beans to your chicken or you can just spread black beans in a "line" sort of over the center of the enchiladas in the pan. Pour on white sauce, top with remaining cheese, bake at 350 F. for 30 minutes.
It might look complicated but it's really easy!
Forgot to say I make pico de gallo to serve with this. I cooked this for about 80 people one night and made gazpacho - they used it like salsa and poured it on these - it was pretty good