What is the "grated yam" in okonomiyaki?
Wikipedia lists "grated yam" as an ingredient of okonomiyaki. Is it a particular type of yam? Can it be purchased outside of Japan?
== More Info ==
As Mein suggested, I did some more searching on Wikipedia and the internets.
The "yam" in question is Dioscorea opposita or Japanese mountain yam. In Japanese it is known as yamaimo (kanji: 山芋; hiragana: やまいも).
Unlike other yam varieties, dioscorea opposita doesn't need to be cooked before consumption. (Most yams contain harmful substances in their raw state.) The dioscorea opposita still contains "oxalate crystals" in the skin which can irritate the skin.
Image copied from wikipedia
This video shows the yam being grated. I've seen this yam grated before and the grated result was very slimy and gooey.
The grater used for yamaimo is different to western style graters. Oroshigane graters have small spikes on the grating surface.
There may be more than one variety of Japanese mountain yam. I saw a reference (now lost) to a variety with dark skin.
Best Answer
It's "a slimy potato" - http://en.m.wikipedia.org/wiki/Dioscorea_opposita. It might be available in Asian grocery stores.
You could probably get by without it. Okonomiyaki translates literally as "cook as you like it". It's a savory pancake-like batter, to which is added whatever you want; often whatever you happen to have lying around the kitchen. Much like an omelette, okonomiyaki is a pretty free form thing.
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What is okonomiyaki batter made of?
At its simplest, okonomiyaki batter is just flour, eggs and water, though dashi, an intensely savoury, seaweed-based stock often replaces the last.What is okonomiyaki garnish made of?
*Aonori is also known as green laver. It is edible green seaweed, usually consumed as dried, finely flaked form. Often used for Okonomiyaki, Yakisoba, and takoyaki topping in Japanese cuisine. *Pickled ginger can be mixed into the batter or garnish later sprinkling on top of Okonomiyaki.How do you shred cabbage for okonomiyaki?
Shred the cabbage for okonomiyaki The easiest way to do this is to chop the cabbage into large chunks and then use a food processor's shredding attachment to produce thinly-shredded bits of cabbage.What kind of cabbage is used for okonomiyaki?
Core and shred Napa cabbage, then transfer to a large bowl. Use a vegetable peeler to grate the carrot into the same bowl. Thinly slice scallions, adding most to the bowl with the cabbage and carrots. Add ketchup and Worcestershire to a small bowl and mix to combine, then set aside.Grating Yama-Imo Yam for Okonomiyaki
More answers regarding what is the "grated yam" in okonomiyaki?
Answer 2
You should have searched a bit more on Wikipedia :)
Yam is not the sweet potato most people know in the US, but a kind of root. For the preparation of okonomiyaki it doesn't really matter which one.
I don't know where you can buy this, but my advise is to ask in your grocery store, market or specialized (African or Asian food) shop.
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Images: Ann H, Brett Jordan, Madison Inouye, Prateek Katyal