This is a classic way of eating nagaimo 長芋 or yamaimo 山芋 in Japan. This preparation of grating or "Tororo" トロロ, however, is not for most Western audiences since it is ultimately "slimy". My wife appears to have overcome the sliminess most of the time after gradual conditioning over the years. Although grated nagaimo has right consistency as is, yamaimo tends to become very thick and to eat as "Tororo", it may have to be diluted with dashi (or my mother used to dilute it with miso soup since this was often served as a breakfast item and miso soup was also regularly served for breakfast).
I grated the nagaimo, seasoned with soy sauce with wasabi and chopped scallion. Since I had onsen eggs 温泉卵 which I had made previously sitting in the refrigerator, I dropped that in the middle and garnished it with thin strips of nori seaweed.
When you dig in you see the nice creamy egg yolk. The egg can be poured over rice and enjoyed as is the traditional way, we just ate as a accompaniment for sake. Since the potato has lots of starch, this is surprisingly filling and remarkably went well with sake.