Preheat oven to 400 degrees Fahrenheit (200 degrees Celsius) and grease a 9x13 inch baking dish.
Steam the cauliflower florets for 5 to 7 minutes until tender-crisp, then drain and pat dry to remove all excess moisture.
In a large mixing bowl, beat the softened cream cheese until smooth, then whisk in the buffalo sauce, ranch dressing, garlic powder, salt, and pepper.
Fold the shredded chicken and steamed cauliflower into the cream sauce until thoroughly and evenly coated.
Transfer the mixture to the prepared baking dish and spread into an even layer.
Sprinkle the shredded cheddar cheese and blue cheese crumbles uniformly over the top.
Bake for 20 to 25 minutes until the cheese is melted, golden-brown in spots, and the sauce is bubbling at the edges.
Remove from the oven and garnish with sliced green onions. Let stand for 5 minutes before serving.