Prep the oven and pan: Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with a little butter or nonstick spray.
Par-cook the cauliflower: Steam or microwave the cauliflower florets until just tender, about 4–5 minutes. Drain well and pat dry with paper towels to remove excess moisture.
Sauté aromatics: In a skillet over medium heat, melt the butter.
Add the red onion and celery. Cook 3–4 minutes until softened. Turn off the heat and set aside.
Make the buffalo dip base: In a large bowl, mix cream cheese, hot sauce, ranch dressing, and sour cream until smooth.
Stir in garlic powder, onion powder, smoked paprika, and a pinch of salt and pepper.
Add chicken and veggies: Fold the shredded chicken, sautéed onion and celery, and the cauliflower into the buffalo mixture until evenly coated.
Add cheese: Stir in half the mozzarella and half the cheddar. Transfer the mixture to the prepared baking dish and smooth the top. Sprinkle the remaining cheeses over the surface.
Bake: Bake for 20–25 minutes, until bubbly around the edges and the cheese on top is melted and lightly golden.
Rest and garnish: Let it rest for 5–10 minutes to set.
Top with sliced green onions and parsley. Taste and adjust salt and pepper if needed.
Serve: Scoop into bowls and enjoy as-is, or pair with crisp cucumber slices, celery sticks, or a simple side salad.