• Preheat oven to 350°F Coat a 9x13-inch oven-proof casserole dish with oil spray.

For the Sauce:

• In a small pan set over medium-low heat, add 1 tablespoon of the butter and when it has melted add the grated garlic. Sauté the garlic for about 30 seconds. Do not let it brown.
• Add the remaining butter, garlic powder, salt and pepper and cook only until the butter is melted.  
• Stir the flour into the butter making a roux and cook for 1-2 minutes.  Gradually add the chicken broth whisking to combine. Continue to whisk until smooth and creamy, then whisk in the sour cream until smooth. Set aside to cool.

For the Filling:

• in a large skillet set over medium heat add the oil and when it has warmed add the onion and red pepper. Sauté just until the onion has softened. 
• Remove from the heat and add the shredded chicken, green chilies and cooled sauce.
• Stir in enough of the chicken broth to make the filling thick and spoonable.   Add salt and pepper to taste.

To Assemble the Casserole:

• Place 6 of the tortillas on the bottom of the casserole dish and add 1/2 of the chicken mixture and 1/2 of the Monterey Jack Cheese and 1/2 of the cheddar cheese.  Repeat with a second layer.
• Spray a piece of aluminum foil with non-stick oil spray and cover the casserole, sprayed side down.  
• Place the casserole in the oven and bake for 30 minutes; then remove the foil and continue to bake for another 10 minutes until golden brown and bubbly at the edges. Transfer from the oven and allow to cool for 5 minutes.