In a medium bowl, combine the shredded chicken and BBQ sauce. Mix well until the chicken is fully coated. Season with salt and pepper to taste.
Heat a skillet over medium heat. While the skillet is heating, butter one side of each slice of bread.
Place one slice of bread, buttered side down, in the skillet. Layer half of the cheddar cheese on top.
Spread the BBQ chicken mixture evenly over the cheese, then top with the remaining cheese.
Place the second slice of bread on top, buttered side up. Cook for about 3-4 minutes until the bottom is golden brown.
Carefully flip the sandwich and cook for another 3-4 minutes until the other side is golden brown and the cheese is melted.
Remove from the skillet, let cool for a minute, then slice in half and serve warm.