Warm the sauce. To a medium saucepot over medium-low heat add the cubed cream cheese, ranch dressing, hot sauce, black pepper, and garlic powder. Whisk constantly until the cream cheese has dissolved in the ranch and hot sauce. Remove from heat.
Combine. Add the cooked and shredded chicken, green onion, 1 cup of the shredded mozzarella cheese, and one cup of the shredded cheddar cheese to the saucepot. Mix well to combine. Transfer to your prepared baking pan and top with remaining mozzarella and cheddar cheese.
Bake. Bake for approximately 20-30 minutes, or until the cheese has melted and the sides are starting to bubble. Set oven to BROIL. Allow your buffalo chicken dip to cook for an additional 2-3 minutes, or until the top is golden brown. Remove it immediately.