Shred both kinds of cheese, or get already shredded one, and mix them together. Make sure to have enough for topping. You will need a little less than a ½ cup to sprinkle on top of the potatoes before baking. You can certainly use any cheese that you prefer or like, or perhaps have on hand. I think cheddar is quite amazing and compliments potatoes very well. You can also add hot sauce to the mixture, like a buffalo sauce or sriracha. The chicken could make a potato mixture pretty dry, so make sure to add that butter and sour cream as well as milk to keep it from drying.