Carp is cut into pieces. (photo: VOV)

The first step is to choose the fish. It should be a fish caught in a river or lake or raised in a pond on organic feed.  The fish can be carp, grass carp, or crucian carp. Big fish have firm, delicious meat. Other ingredients are galangal, garlic, salt, and “thinh”.  Thinh is made by roasting rice over a medium heat until golden. When it cools, the roasted rice is ground to a fine powder.

Fish are cleaned well to eliminate the fishy smell, and cut into pieces to blend with finely chopped galangal and garlic, salt, and thinh.

Luong Van Muon of Son La province said: “We mix all the other ingredients together first and then blend the mixture with the fish. The mixture will ferment the fish. If you want to speed up the fermentation, add a little sugar.”

Cover the bottom of a big vase with some of the mixture before putting the fish in to it. The vase is tightly covered to ferment the fish for a week.

Luong Van Muon again: “In the past people fermented fish for longer storage. The longer it is preserved, the tastier the fish is. To keep the sour fish for a long time, you must pay attention to the amount of salt you use. If the salt is too little, the fish will turn sour quickly but can’t be kept for very long. The salt must be just enough.”

Whenever the Thai caught many fish in the river or dredged a pond, they fermented the extra fish to preserve them.

Now they make sour fish to sell to tourists. Sour fish is best with fresh herbs, figs and guava leaves, which have an acrid taste.

Tran Thi Hiep, who was originally from the central province of Ha Tinh, said: “I have lived in Son La province for many years. I’ve eaten many Thai fish dishes. They have a distinctive taste. The sour fish has the delicious taste of fish, galangal, garlic, and thinh.”

A trip to the Thai community in the northwest region is not complete without trying the sour fish.