In general, the Japanese are not great fans of offal, but for
some strange reason this restriction is relaxed for yakitori,
Japanese grilled chicken. At any yakitori joint, you'll find
skewers of skin (kawa), cartilege (nankotsu),
liver (reba), heart (hatsu), tongue (tan),
intestines (shiro) and the mysterious part known only as head meat
(kashira)...
...which, in retrospect, should have prepared me for kinkan:
chicken ovaries. This is a bit of a rarity, partly because
you have to disembowel two chickens to get one stick's worth, but
it's worth looking out for. The ovary itself is a scrawny runt
of an organ that tastes just like chicken; perhaps more interesting
is that there is usually a half-developed egg still attached,
with no shell and the egg white and yolk still undifferentiated,
making it a yummy treat.
Incidentally, kinkan also means kumquat, so being offered
kinkan ice cream is not necessarily reason to run away
screaming. (At least until you find out which ingredient they're
using. This is less funny than it might seen: Japan is not only
the country of the squid pizza, but also the
country of egg, wasabi and natto-flavored ice cream...)