Add butter to a skillet over medium high heat. Stir in the peppers, onions and garlic. Cook until softened.
Transfer the vegetables to a bowl.
Add the chicken to the skillet and cook until warm, approximately 5-6 minutes. Stir in the taco seasoning and 1/4 cup water. Cook for 3-4 minutes. Transfer to a bowl.
Melt the remaining butter in the skillet. Stir in the flour and cook for 2-3 minutes or until it begins to turn golden brown.
Whisk in the chicken stock and bring to a boil. Stir in the garlic powder, onion powder, cumin, chili powder and canned tomatoes.
Turn the heat off. Stir in the half and half and cream cheese until melted. Add 1 cup of cheddar and stir until melted.
Add 1/3 of the Doritos to a 9 x 13 inch baking dish coated with cooking spray. Arrange 1/2 the chicken in an even layer over the Doritos and top with 1/2 the vegetables. Top with 1/3 of the Doritos. Arrange 1/2 the chicken over the layer of chips and then top with the vegetables.
Pour the cream sauce over the casserole and mix it in with a spatula just a bit so it can work it's way down to the bottom of the dish.
Arrange the remaining Doritos over the top of the casserole and sprinkle with the rest of the cheddar cheese.
Bake the casserole, uncovered, for 30 minutes. Allow to cool for 10 minutes before serving.
Serve with chopped cilantro, sour cream and salsa, if desired.
Notes
Dorito Chicken Casserole recipe can be assembled in advanced and stored in the refrigerator covered tightly with plastic wrap.To bake, remove the plastic wrap and bake according to recipe instructions.