Add a couple bacon slices for smokiness (and, of course, meatiness!).
Instructions:
Butter slices of good-quality sourdough bread. Layer Gruyère cheese and thinly sliced tart apples and top with another slice of the buttered bread. Cook the sandwiches in a few tablespoons of melted butter – you can use a press or an ordinary skillet with a bit of weight on top of the sandwich – turning once, until the cheese has melted and the bread is golden brown on both sides, about eight minutes total.