In a medium bowl, combine the shredded chicken and buffalo sauce. Mix until the chicken is well coated.
Heat a skillet over medium heat and add 1 tablespoon of butter.
Place two slices of bread in the skillet. Top each slice with a slice of cheddar cheese, followed by the buffalo chicken mixture, and then another slice of cheddar cheese.
Top with the remaining two slices of bread. Cook until the bottom is golden brown, about 3-4 minutes.
Carefully flip the sandwiches and add the remaining tablespoon of butter to the skillet. Cook the other side until golden brown and the cheese is melted, about another 3-4 minutes.
Remove from the skillet and let cool for a minute. Slice in half and serve with ranch dressing and blue cheese crumbles, if desired.