Taco Casserole

I made this a while ago but I'm still trying to catch up. This recipe is from our school cookbook but is also one of my really good friends recipe, thanks Susan :) My family really enjoyed this dinner, I especially did. I really love Mexican food, I never thought I would say that but that's due to really never trying any when I was younger. This picture doesn't actually give this meal justice because it was super good and really easy to make aswell.
2 lbs. hamburger
1/2 onion, chopped
2 (10 3/4 oz.) cans cream of mushroom soup
10-12 (6-inch) corn tortillas
1/2 can diced green chilies
1/2 pkg. taco mix
grated cheese (about 2 c.)

Brown hamburger with chopped onions. Drain grease and add chilies, soup and taco mix. Layer in a casserole dish, start with quartered tortillas, then hamburger mixture, then cheese and repeat. Bake for 20 minutes at 350F. Serve with grated cheese, tomatoes, lettuce and sour cream (whatever you like).