In a 9x12 pan, place 4 tortilla shells on bottom and up the sides of the pan (it helps to spray the pan with cooking spray).
In a large bowl, mix the chicken, onion, soup, and chiles well.
Spread half the mixture on top of the 4 tortilla shells.
Add another layer of 3 tortilla shells.
Spread remaining chicken mixture on top.
Add remaining 2 cups of shredded cheese.
Cut the last tortilla into 1/2" strips and place in lattice design on top of cheese.
Bake uncovered at 350 degrees for 35 minutes or until browned.