Preheat the oven to 400°F (200°C). Butter a 10-inch ovenproof skillet or a similar baking dish.
In a mixing bowl, combine the room-temperature cream cheese, cooked shredded chicken, corn, buffalo sauce, chopped cilantro, and chopped green onions.
Add the crumbled blue cheese (if using) and the ranch dressing to the bowl. Season with black pepper and stir until the mixture is smooth and creamy.
Spoon the dip into the prepared skillet or baking dish and spread it into an even layer.
Top the dip with the shredded cheddar and shredded pepper jack or Colby Jack cheeses.
Bake for 20 minutes, until the cheese is melted and bubbly. If desired, broil 1–2 minutes to brown the top—watch closely.
Remove from the oven, sprinkle with extra chopped cilantro or green onions if desired, and serve warm with hard pretzel twists.