01 - Combine shredded chicken with buffalo wing sauce and melted butter in a mixing bowl. Toss until meat is evenly coated. Reserve until ready to assemble.
02 - Lay out bread slices on a cutting board. With a spatula, spread softened butter on one side of each slice.
03 - On the unbuttered side of 4 bread slices, evenly distribute shredded cheddar and mozzarella cheeses. Top with buffalo chicken mixture, then sprinkle with blue cheese crumble and green onions if desired.
04 - Cover each prepared sandwich base with a remaining bread slice, placing the buttered side outward.
05 - Preheat a large skillet or griddle over medium heat. Place sandwiches in the pan and cook for 3 to 4 minutes each side, pressing gently, until bread is golden and cheese is fully melted.
06 - Transfer sandwiches to a cutting board, rest for 1 minute before slicing. Serve warm with ranch or blue cheese dressing as a dipping sauce.