Preheat and prep: Heat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with cooking spray or a little butter.
Cook the base: Boil the pasta in salted water until just al dente.
Drain well. If using diced cooked potatoes instead, make sure they’re tender but not falling apart.
Make the Buffalo sauce: In a large bowl, whisk together hot sauce, ranch, cream cheese, and sour cream until smooth. Add garlic powder, onion powder, smoked paprika, salt, and pepper.
Taste and adjust heat by adding more hot sauce if needed.
Combine with chicken: Stir the cooked chicken into the sauce until evenly coated.
Add cheeses and pasta: Fold in 1 cup cheddar and all the Monterey Jack. Gently mix in the pasta (or potatoes) until everything is well combined.
Assemble: Pour the mixture into the prepared baking dish. Sprinkle the remaining 1/2 cup cheddar over the top.
If you like blue cheese, scatter it over now.
Make the crunchy topping: In a small bowl, mix panko with melted butter and a pinch of salt. Sprinkle evenly over the casserole.
Bake: Bake for 20–25 minutes, until the edges are bubbling and the top is golden. If the topping needs more color, broil for 1–2 minutes, watching closely.
Rest and finish: Let the casserole sit for 5–10 minutes so it sets slightly.
Garnish with green onions and a little chopped celery for fresh crunch.
Serve: Drizzle with extra hot sauce or ranch if you like. Scoop into bowls and enjoy warm.