Leave it to a Japanese to not know shit about potatoes. I bet he could have held a 2 hours lecture on rice extempore, no problem. The Japanese eat everything imaginable and unimaginable you can find in the ocean, but on land they can only imagine rice, which is best exemplified by their language in which cooked rice and meal share the same word. Even in Ireland potato and meal aren't synonyms linguistically (even if they are at the dinner table).