Spread blue cheese dressing evenly on top and bottom slice of bread.
On top of bread, layer chicken, watercress, celery and walnuts. Add second slice of bread.
Heat a panini maker or sandwich press.
Butter each side of the press.
Place the sandwich inside, press down and grill until the bread is flat and browned, approximately 20 minutes.
Serving Suggestion: Stop by your nearest craft or hardware store and pick up a piece of synthetic grass roughly the size of your serving table. Use white paint and numbered stencils to add horizontal lines and field numbers to create a football field design. Add the Buffalo Chicken sandwiches on a football shaped tray, and other themed pieces, and you will have a game day display your guests will cheer about!