In a large skillet over medium heat, saute onions in oil until softened, about 5 minutes. Add garlic and cook another minute. Add in flour and cook another minute. Stir in milk, cumin, cayenne pepper sauce and simmer until thickened. Remove from heat and add sour cream and green chiles.
Layer in a 9 by 13 inch pan: ½ cup skillet sauce; 1 cup of tortilla chips, 1 cup of chicken, 1 cup of skillet sauce, ⅔ cup cheeses, a tablespoon of green onions, about ½ cup of enchilada sauce. Repeat twice for three layers.
Bake for 30 minutes, or until bubbly. Sprinkle with additional green onions.
Recipe by Everyday Southwest at https://www.everydaysouthwest.com/chicken-green-chile-casserole-lightened-up/