This fish noodle soup is originated from Quỳnh Côi, a town in Thái Bình province in northern Vietnam, where is is simply called canh cá (literally mean fish soup). The Quỳnh Côi fish noodle soup is cooked with fried or roasted climbing perch (Vietnamese: cá rô), and served with a flat and broad rice noodle, which is called bánh đa in Vietnamese. Modern adaptions may use bún, a more common rice noodle in Vietnam. Fishcakes made from the same fish are also seen in some modern restaurants. Sometimes the dish is referred as bánh đa cá rô or bún cá rô. The Quỳnh Côi fish soup has been recorded in the list of typical Thái Bình delicacies since around the 17th century.
The dish can be found in some local Vietnamese restaurants which sell only this dish. It’s rarely made in home because the cooking methods requires many steps.
The climbing perch (Anabas testudineus) is a type species of fish of the genus Anabas in the family Anabantidae (the climbing gouramis). It is small in size but is prized in Vietnam for its aromatic meat.
The climbing perch is often poached or blanched to get the meat or you may call the fish fillets. The heads and bones can be used in the fish stock. Fish fillets will then be marinated, slightly roasted and slow-fried.
The broth can be cooked with the pounded heads and bones of climbing perch, but it may not adequate to make a savory soup. So, in commercial restaurants, pork stock is often used, and the broth is a mixture of pork stock and fish stock.
The original Quỳnh Côi fish noodle soup calls for a white flat noodle soup, which is similar the pho noodle, but thinner. A close substitution is a reddish-brown one, which is called bánh đa đỏ. All these two flat types of noodle are more readily available in northern Vietnam, so in southern Vietnam, the soup is served with bún, common Vietnamese soft rice vermicelli.
Raw or quick-poached vegetables used together with this soup can be adjusted based their seasonal availability. Common choices are baby mustard greens (5-8 cm/2-3 inch in length), radish sprouts or seedlings (5-7 days old), and water celeries.
Shake the climbing perch with some rock salt to reduce the slime. Rub the fish with lime juice, and rinse with rice-rinsing water (or you can mix some starch in water). Rinse again with water.
Marinate the fish fillets with pounded galanga, ginger, minced shallots and 3 tablespoons of fish sauce for about 30 mins.
If you have time, soak the pork bones in warm water with a little salt to clean off the blood, then rinse. Then, blanch the bones for 3-4 minutes to remove impurities, rinse. Add the pork bones into a pot of water, and slow-cook for 2-3 hours. Skim occasionally for make sure the pork stock is clear. Season with some salt. Finally, drain for the pork stock.
Put the fish bones in a new pot with a little crushed ginger, a little salt. Bring to a boil, then switch to simmering, do not stir to avoid crushing the fish. Occasionally skim off the foam. Simmer for 1-2 hours, then filter through a sieve to get the clear fish stock. Combine the fish stock and pork stock, bring to a boil. Re-season to taste.
Blanch a strainer spoon of rice noodle, and place it in a serving bowl. Add the fish fillets, pour the broth. Serve with pickled bamboo shoots and a dish of poached or raw baby mustard greens.
Curcumin powder is only the second choice if you can't find fresh turmeric.
You can try filleting the fish without poaching them.