Cheese is arguably the highlight of any grilled cheese sandwich, but that’s not to say other ingredients can’t—or shouldn’t—make some cameos. Just make sure whatever you add enhances your preferred cheese and bread without overpowering them. Take Swiss, for example. It works well on toasted wheat, but can fall flat without anything else next to it. That’s where a bright, crunchy apple might come into play—the acidity is a perfect complement to the generally mild character of Swiss. A cheddar, say, works well with prosciutto and bacon, which possess smoky undertones that bring out the cheese’s sharpness and are both thin enough to let the cheese itself shine. For something more offbeat, try sage leaves or sliced figs, which tend to bring out the luscious, gamey qualities of goat’s cheese, or sliced portobello and a little guacamole, which works well with pepper jack. Whatever you do, don’t pile on heavier meats or even deli like sliced turkey—it’s a main ingredient, after all, and only turns your elevated grilled cheese into, well, a turkey sandwich.