Preheat your oven to 350 degrees Fahrenheit.
In a large bowl, combine the diced chicken and buffalo sauce. Stir until nicely coated.
In a separate medium bowl, blend together the softened cream cheese, sour cream, and garlic powder until fluffy.
Add the buffalo chicken mixture and diced green onions to the cream cheese blend. Fold in half of the shredded cheddar cheese.
Spread the combined mixture into a greased 9x9 baking pan. Top with the remaining cheddar and mozzarella cheeses.
Bake for about 20 minutes or until bubbly and golden brown on top.
Remove from the oven and serve hot with chips, baguette slices, crackers, or celery sticks.