Heat oven to 375°F (190°C). Lightly butter or spray a 1-quart (1 L) baking dish or 9-inch pie dish.
Make the base. In a bowl, whisk cream cheese (softened), buffalo hot sauce, and ranch or blue cheese dressing until ultra-smooth. Whisk in melted butter.
Fold in cheeses & chicken. Stir in cheddar, Monterey Jack, blue cheese crumbles (if using), scallions, and the shredded chicken. Season with a pinch of salt and pepper (remember: the hot sauce and cheese are salty).
Bake. Spread evenly in the dish. Bake 20–25 minutes until bubbling at the edges and lightly bronzed on top.
Finish & serve. Rest 5 minutes (it thickens slightly). Top with extra scallions. Serve your buffalo chicken dip hot with crunchy veg and chips.