Mau son (mẫu sơn) is a Vietnamese rice wine that is traditionally made by Dao people who mainly live in the mountainous areas of the province of Lạng Sơn. The drink is distilled from cooked rice, spring water, and a specific type of yeast that is made with various herbs and plants.
Because of the cold weather, the fermentation takes place over several weeks, before the wine can be distilled. The final version is smooth and potent, but without being overpowering or too harsh, and it will usually have mellow herbaceous aromas.