Soak the black glutinous rice for 2 hours, then rinse well. Cook in a rice cooker with enough water to cover the rice by about 1 inch (2.5 cm).

When the rice is cooked, spread it out on a tray to cool until just warm. Crush the yeast balls and sprinkle evenly over the rice, then mix well.

Pack the rice tightly into a large bowl, cover the surface completely, then place the bowl in a pot or container. Cover the top with a towel to keep it warm for several days.

After 5 days, uncover. The rice should have a fragrant wine aroma and is ready to eat.