Place a small skillet over medium heat and add the butter. Once the butter is melted add in the onions. Cook until softened, 4-5 minutes. Add garlic and cook for 1 minute. Remove from heat.
Add the cream of chicken soup, sour cream, 1 cup of cheese, and taco seasoning to a large mixing bowl. Stir to combine.
Add the chopped chicken, Rotel tomatoes, green chiles, black beans, corn, onions, and garlic to the mixing bowl. Stir until evenly combined.
Leave the Doritos in a bag and use your hands to crush them up a bit. You don’t want tiny crumbs, just medium-sized pieces.
Spread half of the crushed Doritos in the bottom of a 9x13 baking dish. Spoon the chicken mixture over the chips and spread into an even layer. Don’t just dump it from the bowl or the chips may get pushed out of the way.
Bake for 20 minutes. Remove the casserole from the oven. Top with the remaining Doritos in an even layer and then sprinkle with cheese. You can use as much or as little as you like.
Return the casserole to the oven and cook for 5 more minutes, or until the cheese has melted
Sprinkle the casserole with chopped parsley. Cut into 6 portions and serve warm. We like to add a dollop of sour cream on top of each portion.
I used one whole store-bought rotisserie chicken with the skin removed. You could also use 2 boneless skinless chicken breasts that you cooked ahead of time.