Preheat oven to 350 degrees. Heat your Green Chile sauce in a saucepan just till heated thru. Start by scooping a little sauce in the bottom of your casserole dish, then lay your corn tortillas, flat not rolled, on top of the sauce. Start your layering your goodies. Chicken, onions, black beans, a little green chile sauce. Add 2 more corn tortillas on top of your finished layers, spoon the Green Chile Sauce liberally over the top and then sprinkle the entire casserole with cheese. Spoon a little more green chile sauce on top of cheese, (if you have room!). and Bake 30 minutes or until heated thru and the cheese is bubbly.