Preheat the oven: Set to 375°F (190°C).
Lightly grease a 9x13-inch baking dish with olive oil or butter.
Prep the chicken: Shred the cooked chicken into bite-size pieces. If it’s cold, let it sit out for 10 minutes so it mixes more easily.
Make the creamy base: In a large bowl, mix cream cheese, sour cream, and mayonnaise until smooth. If needed, microwave the cream cheese for 15–20 seconds to soften.
Add the heat and flavor: Stir in buffalo sauce, garlic, onion powder, smoked paprika, and a pinch of salt and pepper.
Taste and adjust the heat level now.
Fold in the cheese: Add half the mozzarella, half the cheddar, and all the blue cheese (if using). Mix until evenly distributed.
Add the chicken and onions: Fold in the shredded chicken and green onions. The mixture should be thick and creamy, not runny.
Assemble: Spread the mixture evenly in the baking dish.
Top with the remaining mozzarella and cheddar.
Bake: Bake for 18–22 minutes, until the edges bubble and the top is melted and lightly golden. For extra color, broil 2–3 minutes at the end—watch closely.
Finish and serve: Let it rest 5–10 minutes to set. Garnish with more green onions and a light drizzle of ranch or blue cheese dressing if you like.