On a lightly floured board, roll 6 thawed frozen puff pastry patty shells (10-oz. package) into 4-inch-wide rounds. Sprinkle each round with 2 tablespoons shredded gruyère or Swiss cheese (3/4 cup total); sprinkle lightly with cayenne. With rolling pin, gently press cheese into pastry. Place rounds slightly apart on a 12- by 17-inch baking sheet. Bake in a 400° oven until browned, 8 to 10 minutes.