My Yuletide match this year was on a particularly esoteric micro-fandom -- and in mystery, rather than SF/fantasy.  This is the story I wrote:

A Matter of Delicacy
Judge Dee mysteries - Robert van Gulik
G •  gen • ~3000 words
Dee Jen-djieh | Di Renjie, Miss Violet Liang, Tao Gan, First Lady, Second Lady, Third Lady, Original Characters

When a memorable figure from Judge Dee's past turns up on the doorstep of the Metropolitan Court, the Lord Chief Justice is confronted with a puzzle whose unraveling may call for a particularly subtle approach -- and whose solution may pose its own challenges for the judge's visitor.

The Judge Dee series takes place in seventh-century China; Robert van Gulik wrote a total of sixteen novels and one set of short stories that are a rather odd mix of historical fact and fiction.  There was a genuine historical "Judge Dee", on whom van Gulik's character is based, and there's a lot of legitimate period detail in the books.  But while the individual mystery scenarios are almost all taken from authentic Chinese sources, van Gulik creates a wholly fictional career for Judge Dee, and the novels' storylines have no basis in specific events.  Also, van Gulik incorporates a degree of deliberate anachronism into the texts, describing cultural elements from the much later Ming dynasty as opposed to those prevalent in seventh-century Tang China.

Yet anachronisms notwithstanding, the series -- originally published in the 1960s and '70s, but still in print today (!) -- makes for fascinating reading.  Van Gulik was a native Dutchman who served as his country's ambassador to China, and published a fair bit of (somewhat esoteric) scholarly writing on Chinese culture in addition to his fiction, but it's the Judge Dee stories for which he remains best known.

My own story, at its recipient's suggestion, picks up on the status of a character featured in one of the series' middle books -- a female wrestler and martial-arts tutor from Mongolia -- and looks in on that character again about a decade later.  In the course of developing the story, I reread the whole canon (some volumes more than once), and consulted a variety of printed and online reference material -- establishing, in the process, that most of what I knew about Chinese history I'd originally learned from reading the Judge Dee books.  (Heh.)

Not surprisingly, the story has picked up a fairly small number of hits and garnered little to no notice in the wider Yuletide gossip mill.  Which is just fine; that's why it's called a micro-fandom.  (I write in a lot of these....)  The important bit is that my recipient is happy -- which she is, judging by the comment in response -- and thus I am well satisfied.