Sour fish soup or ‘suan tang yu’ is a study in rustic, wholesome cooking. In Beijing, live freshwater fish is cooked with salted and pickled vegetables, and wood ear fungus in a basic pork stock. The flavours seep out of the pickles, infusing the fish with a pungent sourness, and the peppercorns add a spicy zing that lifts the sourness. I refined the dish using fish fillets instead of a whole fish and baby wood ear fungus.
Wood ear fungus20g (⅔oz), soaked in water until soft and cut into strips
Tomatoes20g (⅔oz), seeded and cut into strips
Fresh or canned bamboo shoot20g (⅔oz), cut into strips
Cooking oil500ml (16fl oz / 2cups)
Prepare fish stock. Heat cooking oil for deep-frying and fry fish bones until golden brown. Drain and set aside. Reserve a little oil in wok and sauté white peppercorns until fragrant.
In a deep pot, place water, fried fish bones, fried peppercorns, ginger, spring onions, coriander, carrot and celery. Bring to the boil, then reduce heat and simmer for 1 hour. Strain and discard ingredients.
While fish stock is cooking, preheat oven to 70°C (146°F). Fillet carp and remove fish skin. Cut skin into 12 × 2.5-cm (5 x 1-in) strips and marinate with salt. Arrange strips on a baking tray and bake for about 20 minutes or until skin is dry to the touch. Set aside.
Cut fillet into 60g (2oz) pieces. Marinate with salt and cooking wine and leave for 2 minutes.
Reheat 150 ml (5⅓ fl oz) fish stock over low heat and add gherkins, pickled vegetables, wood ear fungus, tomatoes, bamboo shoots and fish. Simmer until fish is cooked through. Season with fish sauce, salt, pepper, lime juice and white vinegar to taste. Divide ingredients into individual serving bowls, then ladle remaining stock over.
Heat oil in a wok over low heat and deep-fry dried fish skin until crispy. Drain on absorbent paper. Garnish soup as desired and serve immediately, with crispy fish skin.