Preheat your oven to 350°F.
Melt butter in a medium skillet over medium heat. Cook onions for 4-5 minutes. Cook garlic for one minute. Cool.
Mix soup, sour cream, cheese, and taco seasoning in a large bowl. Mix.
Mix chopped chicken, Rotel tomatoes, green chiles, black beans, corn, onions, and garlic in a bowl. Mix well.
Crush Doritos in a bag. Not crumbs.
Spread half of the crumbled Doritos in a 9×13 baking dish, then evenly pour the chicken mixture on top. Pouring from the dish will break the chips.
20-minute bake. After baking, remove the casserole. Top with the remaining Doritos and cheese. Cheese is unlimited.
Return Pioneer Woman Chicken Dorito Casserole to the oven for 5 minutes to melt the cheese.
Serve warm with minced parsley and sour cream, if desired.