In a large bowl, combine the shredded chicken, cream cheese, ranch dressing, Buffalo sauce, black pepper, ½ cup Colby Jack cheese, and ½ cup cheddar cheese. Mix until well combined.
Transfer the mixture to a cast iron skillet and spread it into an even layer.
Top with the remaining Colby Jack and cheddar cheese.
Place the skillet in the Blackstone Pizza Oven and cook for about 8 minutes, or until the dip is hot and bubbly and the cheese is melted with golden-brown spots.
Carefully remove the skillet from the oven and let it cool for a couple of minutes.
Garnish with chopped chives and serve warm with tortilla chips.
