You may have seen these long, light-skinned, and hairy roots at your Japanese or Chinese markets and wondered about their relation to other kinds of tubers. Naga-imo is a kind of mountain yam, the tuberous root of a climbing vine. There are other mountain yams, such as icho-imo, yamamot-imo, tsukune-imo. Mountain yams take on a gluey, almost mucilaginous consistency when they're grated.
But, grating the mountain yam immediately transforms it from a fairly common-looking root vegetable into a pile of sloppy white goo. This fact alone makes naga-imo and other mountain yams distinct from tubers such as the potato or taro, not to mention the unique taste and texture.
Mildly sweet like jicama with a texture similar to taro, only less starchy, naga-imo is delicious pan-fried until the surface is browned and crisp and the interior is soft and tender. This is the way I usually eat naga-imo: after browning some bacon in the cast iron, I use the bacon fat to cook thin slices of naga-imo, and call it a day.
But sometimes I'm inclined to go a step further and take advantage of naga-imo's unique texture. Grated naga-imo is a common ingredient in Japanese dishes that require a binder such as okonomiyaki, a kind of pancake layered with cabbage and often pork belly. I don't often go through the rigmarole of making okonomiyaki by shredding cabbage, browning belly or bacon, sprinkling dashi flakes on top, and dousing the pancake with kewpie mayoinaise and okonomiyaki sauce, yet the idea of using grated naga-imo as a base for a pancake batter is simple enough to do any weeknight.
To prepare the batter, grate the naga-imo with a microplane grater. You can use a bit of potato starch or rice flour if you want to refrain from dairy, but mixing an egg with the grated naga-imo produces just the right consistency for dropping the batter by dollops into your pan. You can add anything you want: chopped bits of bacon, browned garlic and scallions, or sauteed vegetables. If you happen to have fresh herbs around, like basil, mint, cilantro, all the better.
The texture of the batter when it's cooked is something like the interior of a really tender latke, but with very little fuss. Serve with a bit of fine quality soy sauce and sesame oil, and you've got a naturally gluten-free pancake dish.
Finally, a warning: like taro, the skin of naga-imo causes mild itching on the skin, so use a pair of gloves when handling the root.