I believe it's a broad, round bun with a line of cheese dividing it down the middle.

All Ports --Vintage, Tawny, Ruby, what have you-- complement a good Stilton. Something about the salt of the cheese and sweetness of the wine works magic. Other dessert wines will probably be good as well (Roquefort is a good match with Sauternes), but Ports seem to have a special affinity for this cheese.
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Cheers.