Set an oven rack 4-inches below the broiler and set the broiler to 400°F.
Place a cast iron skillet over medium heat. Add the butter.
When the butter is melted, add the garlic and black pepper. Mix together.
Add the hot sauce and stir into the butter.
When the hot sauce is warm, add the shredded chicken breast and stir to completely coat in the hot sauce
Add the cream cheese, a 1/2 cup of the mozzarella cheese, and the ranch dressing. Stir together until the cheese is melted.
If desired, add 1/4 teaspoon or more of cayenne pepper to the dip.
Turn off the heat and sprinkle the remaining mozzarella cheese over the top.
Transfer the skillet to the oven. Broil until the mozzarella cheese starts to brown and bubble.
Remove from the oven, and sprinkle the crumbled blue cheese and sliced green onions over the dip.