An essential ingredient in okonomiyaki is some grated nagaimo in the raw batter. Often found in Asian markets packaged in shrinkwrapped styrofoam or packed in sawdust, nagaimo is a type of yam that is very long and tubular. It's cut in five to six-inch sections before being packaged. It's one of the few members of the yam family that can be eaten raw.
The outside skin is light brown in color and has hairy roots protruding from tiny knobs on the surface. The skin is peeled off, revealing a white flesh that is crunchy and watery like a jicama, but has a very slimy texture. This can make it hard to grip the yam when grating, so take care to not slip and cut your fingers. Some people find that the mucus gives their skin a little bit of an itchy feeling. I haven't noticed this personally. There are some Asian cultures that consider nagaimo to be an aphrodisiac.
Apart from being used in okonomiyaki, nagaimo root is also grated and added to noodles, soups, and maki rolls.
(Image: Kathryn Hill)

Comments (5)
Yamaimo! Yuck! Double, triple yuck!!
When I'm letting Japanes folks decide what I'm going to eat (as in omakase) I make it clear that "nebaneba-mono" are off limits. Yamaimo is nebaneba! Slimy. digusting. tasteless. Warning lights should start flashing, that loud honking should start sounding, whenever, whereever it is found.
I love yamaimo! You can also thinly slice it, pour a little bit of soy sauce, throw some maguro (raw tuna) and eat with rice.
It can leave your hands itchy, so i usually hold the ends with a plastic wrap.
While I agree that grated yamaimo is slimy and kind of gross, I concur that when it's sliced and dipped in soy sauce it becomes quite enjoyable. I refused to go near the thing until my aunt served it sliced once. There's a bit of slime, but it's nice and crunchy and perfect contrast to warm rice.
it's *sort of* considered an aphrodisiac. . . it's recommended in Eastern medicine as a food to increase fertility.
Love love love yamaimo! I love the neba neba. Can't get enough of it. Love it grated or cut into matchsticks and eaten with shoyu or ponzu or mentsuyu.
I just wish it was more readily available in NYC and not so expensive.