Preheat your oven to 350°F (175°C). Lightly grease a medium baking dish with nonstick spray or a bit of oil.
In a large mixing bowl, blend the cream cheese and sour cream until smooth. Stir in buffalo sauce, salt, and pepper. If you like extra tang, add a splash of ranch dressing or a pinch more of buffalo sauce.
Fold in the shredded chicken, cauliflower rice, celery, and green onions. Mix until everything is evenly coated with the creamy buffalo mixture.
Pour the mixture into the prepared dish. Sprinkle half of the cheddar cheese over the top, then finish with the remaining cheddar.
Bake for 20 to 25 minutes, until the casserole is bubbling and the cheese is melted and slightly golden. If you want a crustier top, you can broil for 1–2 minutes at the end, watching closely.
Remove from the oven and let it rest for 5 minutes. Serve hot, with extra celery sticks or a side salad if you like.