Rich with contrasts, this soup is easy to like. The tamarind and pineapple provide a sweet-and-sour edge, while the okra, tomato, and bean sprouts offer spongy, soft, and crunchy textures. The catfish and cumin ground the dish with their pungent, earthy qualities. If rice paddy herb (rau om) is available, use it for a citrusy accent. Sour fish soups are eaten throughout Southeast Asia. The Viet version often includes sliced taro stems (bac ha), a flavorless ingredient known for its ability to absorb other flavors. I generally omit the stems because they don’t contribute much to the soup, and instead increase the amount of okra, which is added at the end. If you can’t find fresh okra, use frozen whole okra, thawing it and slicing it before you add it to the pan. When fresh or frozen pineapple isn’t around, don’t resort to canned. It is not the same. The soup will be a bit tangier but equally sensational without the pineapple.
For sour shrimp soup (canh chua tom), use 3/4 pound medium shrimp, peeled and deveined, instead of the catfish. Also, the pineapple is not optional. You need it for the extra flavor boost it delivers.
