Wash the mung beans under running water until the water runs clear. Soak in cold water for 1 hour; drain.
In a heavy saucepan, cook the mung beans in 3 1/2 cups water until tender, about 30 minutes. Drain; reserve 1/2 cup cooking liquor. Allow the mung beans to cool slightly before adding the remaining ingredients. Set aside to mellow a few hours, then correct the seasoning and serve at room temperature.