Boiled rice and pork cakes are usually cooked 2-3 days before Tet. Both can be kept for about two weeks in cool temperature. However, after this time they become hard and must be re-boiled.
Soak some green beans overnight in water to soften. Drain, rub and clean to remove the skin, and leave to dry. Next, cook the beans in a steamer and grind. Form into balls the size of tennis balls.
Soak some glutinous rice overnight. Clean and rinse. Mix with a little salt. Cut fresh pork meat (lean or fat, according to personal taste) into 2cm strips. Mix with salt, fish sauce and pepper, and leave for about one hour.
Clean dong leaves (leaves from arrowroot) and place them over each other to form a cross. Place an amount of rice in the centre of the leaves. Shape into a square (the southern version is in a circle). Press a "ball" of green bean on top. Then, add 1-2 pieces of marinated pork, then more green bean, and finally rice. Press firmly into a compact square and wrap the leaves over to cover the cake completely. Tie with bamboo strings. Place in a large pot of boiling water and boil overnight. Squeeze the moisture out by placing it in a colander with a heavy object on top.
To serve, untie and open the leaves. Invert on a plate and cut into pieces using the bamboo strings, not a knife. Serve cold.