Preheat oven to 350 degrees F.
Cook the egg noodles according to the package directions. Do not overcook the noodles.
In a large bowl add the sour cream and dip mix, stir together.
Add the cream of chicken soup, Mexican cheese and chicken. Stir everything together. Add the egg noodles and stir together.
Spray a casserole dish with nonstick cooking spray. Add the noodle mixture in an even layer.
Put the crispy onions in a zip up bag. Use a meat mallet or rolling pin to break the onions into smaller pieces.
Top the casserole with the fried onions. Bake for 25 minutes.