Let's start with where the confusion came from. The Polish word ''"śledź"'' (pronounced: {{pron|shletch}}) is the imperative mood of the verb ''"śledzić"'', meaning "to follow", "to trace" or "to spy". But it's also got another meaning, completely unrelated, which would be more fitting in this context: it's "herring". So a better translation of '''''"śledź po japońsku"''''' would have been "herring in the Japanese style". Now what the heck is that?
The "Japanese-style" herring is a very appetising appetiser that was quite popular in Communist Poland. The recipë largely boils down to wrapping a marinated herring fillet around a hard-boiled egg. Perhaps the idea of wrapping a piece of uncooked fish around something reminded someone one Polish chef of ''maki sushi'' rolls, giving rise to its association with Japanese cuisine? Otherwise, this Polish invention has about as much to do with Japan as Hawaiian pizza has to do with Hawaii.
The egg and the fish are typically arranged on a bed of canned green peas laced with mayo and decorated with slices of onions and pickles. The marriage of fishy, salty, sour and fatty flavours means that this simple ''hors d'œuvre'' pairs perfectly with a shot of cold neat vodka.