This rustic soup is originated from some central Vietnamese provinces like Quảng Trị or Quảng Nam. In fact, it is a tribal food of some ethnic minorities like the Cor, Cơ Tu, Xe Đăng, Ca Dong people, but the dish is becoming ubiquitous in those provinces. They also believe the soup is good for breastfeeding mothers. There are two main ingredients: the leaves of Gnetum gnemon and freshwater snails in the genus Sulcospira in the family Pachychilidae.
Gnetum gnemon, gnetum, or woody gnetum, is a tree in the genus Gnetum (unlike most other Gnetum species, which are lianas). Its leaves have some umamai taste and are used as vegetables in mountainous areas and highlands in central Vietnam. Its official Vietnamese name is gắm, but is better known by its local vernacular names like rau ranh, rau bép, lá bép or lá nhíp.
Sulcospira snails are freshwater snails with spiral grooved shapes, and its members usually occur in relatively fast running waters, such as rivers and streams or creeks. Sulcospira snails in Quảng Trị (Sulcospira quangtriensis) and Quảng Nam (Sulcospira tourannensis) are called “ốc đá“, but in some scientific texts, they are referred as “ốc mút” or “ốc vặn”. Of course, some other relatives of these snails (called ốc suối in some other regions), or other freshwater snails might be suitable for this soup. Sulcospira snails are similar to Semisulcospira snails, which are also known to be consumed in Korea.
Soak the snails in a tub of water and crushed chilis for 15-20 mins so that the snails will spit out the dirt. Chop off the pointed end of each snail. Rinse and drain.
Marinate the snails with minced lemongrass, and chili. Add some ground black pepper and salt for about 10 mins.
Heat 2 tablespoons of peanut oil in a pot, then add the marinated snails and stir. Add water, then bring the pot to a boil. Add the gnetum leaves and continue to cook for about 3-5 mins until the leaves lose their original green color. Add the starch flour to thicken the soup. Re-season to taste.
A stir fry version can be done with the same ingredients.