1) Fish 20 Herring in Fang River (near Zenlord).
2) Buy Round Wooden Barrel for 200,000 silver at the Cooking Ingredient Merchant (Martial Artist Sup).
3) Craft Herring Wooden Barrel at the Cook (Martial Artist Min).
4) Go to the marked location (above) and use the barrel on the water to craft Fermented Herring. Upon failure, start over from step 1.
5) After 6 hours, Fermented Herring will turn into Sour Herring Dish which you can consume.