Preheat the oven to 375 degrees Fahrenheit. Shred the rotisserie chicken, discarding the skin.
In a large bowl, combine the shredded chicken with black pepper and garlic powder. Mix well. Add cream cheese to the bowl. Mix until the cream cheese is fully incorporated with the chicken. Pour in hot sauce and ranch dressing. Mix thoroughly until all ingredients are well combined. Add green onions to the mixture and mix again.
In an oven-safe dish or individual bowls, spread the chicken mixture evenly. Top the mixture with a blend of cheddar and mozzarella cheese. Bake in the preheated oven for 20-30 minutes until the dip is hot and bubbly. Optional: To brown the top, increase the oven temperature to 450 degrees Fahrenheit or broil for 5 minutes. Garnish with additional green onions. Serve the Buffalo Chicken Dip with tortilla chips, crackers, or sliced vegetables.
Homemade Ranch Dressing:In a bowl, combine sour cream, mayo, milk, onion powder, dried parsley, salt, garlic powder, dried basil, and black pepper. Whisk the ingredients until smooth and well combined. Use the ranch dressing in the Buffalo Chicken Dip recipe.