In a small bowl, combine chopped chicken, sour cream, cream cheese, buffalo sauce, salt and pepper and mix.
Evenly spread butter on the outsides of the bread. Add about 1/4 of the filling on the inside (non-buttered side) of half of the bread slices. Top with two slices of cheese and then the other piece of bread.
Heat a non-stick pan on medium-low heat. Once warm, place sandwiches on the pan. Do not over crowd the pan.. if you can only do 1-2 at a time, do that! Also, I like to cover the pan with a top while cooking to help the cheese melt.
Cook on each side until golden brown about 2-3 minutes each side. If you notice your bread is turning black turn the heat down to low--you want to have it on the pan long enough for the cheese to melt.
If you're doing 1 or 2 at a time, once you take the finished ones off just cover them with some aluminum foil to keep them warm.
Slice in half and enjoy!