2Make the sauce by melting the butter in a heavy skillet over medium-low heat. Add the garlic, cumin, and chili powder, and saute for a minute or two.Raise heat to medium. Quickly sprinkle in the flour and stir to mix. Pour a small amount of the chicken broth, stirring constantly to remove lumps. Gradually add the remaining chicken broth and the buttermilk and continue stirring until sauce has thickened, 3 or 4 minutes. Add salt and pepper.
3Make the filling by warming a heavy skillet over medium heat. Then adding olive oil. Saute the chopped onion, green pepper, poblano, chiles and tomatoes until onion is transparent, about 4 to 5 min. Add the chicken and green onion to the mix and combine it well.Remove from heat.
4In a small skillet, heat about half an inch of canola oil. Using tongs dip the tortilla in the hot oil one at a time for just a few seconds. Cover the bottom of the baking dish with 4 of the softened tortillas. Layer the remaining ingredients in following order:
Half chicken/ vegetable mixture
Half of grated cheese
Half the sauce
The remaining 4 softened tortillas
the remaining chicken/ vegetable mix
the remaining grated cheese
the remaining sauce
5Bake for 30 min at 350 or until casserole is cook through annd bubbly.