Place a skillet over medium heat and add the butter. Once melted, add in the onions and cook until softened, about 4-5 minutes. Add garlic and cook for 1 minute before removing from the heat.
To a large mixing bowl, add the cream of chicken soup, sour cream, 1 cup of shredded cheese, and the taco seasoning. Stir to combine.
Add the chopped chicken, Rotel tomatoes, green chiles, black beans, corn, onions, and garlic to the mixing bowl. Stir to combine.
Leave the Doritos in a bag and use your hands to crush them up a bit. You want medium-sized pieces, not tiny crumbs. Spread out half of the crushed Doritos in the bottom of a 9-inch x 13-inch baking dish.
Spoon the chicken mixture over the chips and spread into an even layer. (Don’t just dump the bowl onto the chips or it'll push the chips out to the sides.)
Bake for 20 minutes. Remove the casserole from the oven. Top with the remaining Doritos and sprinkle the remaining shredded cheese over the chips.
Return the casserole to the oven and cook for 5 more minutes, or until the cheese has melted.
Remove from the oven and garnish with some chopped parsley. Divide into 6 portions and serve warm. We like to add a dollop of sour cream on top too.
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. You'll need about 3 cups of chicken total.
To make beefy Dorito casserole, cook 1 pound of lean ground beef until browned and cooked through. (Be sure to break up the meat as it cooks.) Drain any excess grease and add it to the recipe instead of the cooked chicken.