Suribachi, Japanese grinding bowl or mortar
When I wrote about essential Japanese cooking equipment a while back, I forgot to mention one item that I use quite often, a suribachi. A suribachi is a sturdy ceramic bowl that's used with a grinding stick called a surikogi like a mortar and pestle. While I'm a big fan of handy electric equipment like food processors for many tasks, sometimes the results you get by doing things by hand are well worth the elbow grease needed.
What makes the suribachi unique, and I think better than a regular mortar, is that the inside is unglazed and grooved, as you can see from the photo below (click on it to see it larger):
The rough-surfaced grooves, which are called kushi no me since they are made with a comb-like device on the wet surface of the clay, help to mash and bruise whatever you are grinding a lot more efficiently than a smooth surface. It's ideal for grinding up sesame seeds, which is what I use it for mostly.
It's also great for making things like peanut sauce - though I do pre-chop the peanuts in the food processor to make things easier. The final grinding in the suribachi seems to really bring out the oils in the nuts, making them so fragrant.
It can be used for grinding up spices too. (My surikogi is stained a bit yellow because I was using it for grinding up some curry spices recently.) The rough grooved surface can also be used for grating soft vegetables like potatoes, wasabi or horseradish root. (Harder and stringier vegetables like carrot and ginger don't grate so well.)
If you do buy a suribachi, try to get the biggest one you can store comfortably in your kitchen. It's much more comfortable to grind up even a small amount in a large bowl. Mine is about 25cm / about 10 inches in diameter. You may see small 'mini suribachi' - these are pretty useless really, though they can make nice individual graters for things like grating fresh wasabi root on the spot. The minimum size for a usable suribachi is around 18cm, or 7 inches.
The first place to look for a suribachi is, as with all Japanese cooking supplies, your local Japanese food store. If you can't find one, I've spotted some on eBay here (a cobalt blue one) and here (a classic brown one). It's also sold on Amazon.com. (None of those merchants ship outside of the U.S. unfortunately.)
See how to grind up sesame seeds to make a paste/sauce in this recipe.