A suribachi is a
Japanese kind of
mortar. Originally it came from Southern
China, it was introduced in Japan between the eleventh and twelfth century. In Japanese cooking, it's used mainly for grinding up
sesame seeds, but also for preparing many kinds of
sauces,
dressings, and
pastes. A suribachi is used in combination with a
surikogi, a wooden
pestle.
A suribachi is an earthenware bowl, glazed (brown) on the outside. On the inside it has a pattern of ridges (ushi-no-me) to facilitate grinding. This pattern can be simply circular (the ridges radiating out from the centre of the bowl), or more elaborate: a pattern made of 'comma's' or even a daisy-wheel design.
Originally, the suribachi was used for grinding miso. Since then, many dishes have been developed for which you need the suribachi: goma-yogoshi (vegetables flavored with a sauce of seasoned, ground sesame), goma-miso (miso flavored with ground sesame), dengaku (sweetened miso sauce used to flavor toasted tofu), kinome-ae (dressing made with sansho sprigs), shira-ae (dressing made of tofu mixed with white sesame), tororo-jiru (grated tororo), tsumire (fish paste balls), denbu (shredded seasoned fish flakes) and kinoton (dumplings covered with ground sesame or soybean powder).
Of course, the suribachi comes in handy too for many other non-japanese dishes, since it's a very efficient grinding tool.
To use it, you place it on a sturdy surface (perhaps with a towel underneath to protect your worktop from the unglazed underside), and use two hands for the surikogi: hold the top of the pestle with one hand and rotate the lower part with the other.