Preheat the oven to 375 F (190 C). Grease a medium-size baking dish or casserole dish so the bottom doesn’t stick.
In a large bowl, mix the shredded chicken with the buffalo sauce. If you like it milder, add a splash of ranch or a little yogurt to balance the heat.
In another bowl, blend the cream cheese, sour cream, and a pinch of salt and pepper until smooth. This will create a creamy base for the casserole.
Fold the creamy base into the buffalo chicken mixture. Stir in the celery and green onions for crunch and brightness.
Spread the mixture evenly in the prepared dish. Sprinkle the cheddar and mozzarella on top. If you’re a blue cheese fan, crumble some on now or reserve for the final topping.
Optionally sprinkle crushed chips on top for a crunchy finish. This is a nice contrast to the creamy filling.
Bake for about 20 to 25 minutes, until the cheese is melted and bubbling and the casserole is heated through. If you’d like the top especially golden, switch to a broil for the last 1 to 2 minutes, watching carefully so it doesn’t burn.
Let the casserole rest for a few minutes. Garnish with fresh cilantro if you like, and serve with celery sticks, carrot sticks, or a simple green salad.