A very dear relative, who was here recently for the Christmas holidays, gave me this recipe for an upscale grilled cheese sandwich. Upscale, perhaps, is the operative word here. Unlike the classic grilled cheese sandwich which uses plain cheddar, this one is made with mozzarella and Gruyère, Italian and Swiss cheeses. But the real surprise in the sandwich is the mango jam. Tart and sweet, it harmonizes with the cheeses to create a perfectly balanced and delectable flavor.