Preheat your oven to 375°F (190°C).
Steam or boil the cauliflower florets until tender, about 5-7 minutes, and drain well.
In a large mixing bowl, combine the cooked chicken, buffalo sauce, ranch dressing, and half the shredded cheese. Mix well.
Add the cauliflower florets to the bowl and gently toss until coated with the mixture.
Transfer the mixture to a greased casserole dish and spread evenly.
Top with the remaining cheese and optional panko breadcrumbs for a crunchy topping.
Bake in the preheated oven for 20-25 minutes, or until bubbly and golden brown on top.
Garnish with green onions before serving.