Cook the chicken. If your chicken is not yet cooked, bring a large pot of water to a boil over high heat. Add the chicken breasts to the pot and return to a boil. Remove from heat and cover with a tight-fitting lid. Allow your chicken to poach, covered, for approximately 25 minutes. When fully cooked, remove from the pot and allow to rest until cool enough to handle (note- the cooking time for the chicken is not included in the total cooking time for this dish).
Prep. Preheat your oven to 350 degrees F. and spray a 9x9-inch baking pan (or approximate size) with non-stick cooking spray.
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 sauce pot. Mix well to combine. Transfer to your prepared baking pan and top with remain 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.
Serve. Serve with tortilla chips, vegetable sticks, crackers, or enjoy leftovers wrapped in a tortilla with all your favorite greens.