I think next time I will add some arugula or spinach or other greens just to have some more *green*.Steak Sandwich1 Ciabatta rollCooked steak, sliced2 tablespoons Gruyere cheese, shredded1/2 medium red onion, thinly sliced1/4 cup mayonnaise1 teaspoon prepared horseradish1 tablespoon parsley, roughly chopped1 teaspoon extra-virgin olive oilkosher salt and freshly ground pepperPreheat a broilerIn a