Start off with your oven by preheating it to 350°F and spray a 9 x 13-inch baking dish with nonstick cooking spray. Cut the cooked chicken into small cubes and set aside.
In a large skillet, melt the butter over medium heat. Add in the chopped onion and garlic clove. Sauté until tender, about 5 minutes. Add in the chicken cubes to the skillet and cook until heated through, about 3 minutes.
In a large bowl, combine the Mexican cheese blend, taco seasoning, cream of chicken soup, black beans, corn, sour cream, Rotel tomatoes, and green chiles. Mix together until combined.
Place crushed Doritos and then pour the mixture into the prepared baking dish. Top with more Doritos and then sprinkle with parsley.
Bake in preheated oven for 25-30 minutes, or until bubbly and golden brown on top. Let cool for 5 minutes before serving