Simmer the mung beans in 1 c cold water for 20 minutes. Drain & set aside. Mix the coconut with the salt, sprinkle evenly n a plate & set aside. In a small pot, over low heat, toast the sesame seeds until light brown. Mix the seeds into the sugar evenly spread on the dish & set aside. In a large bowl, mix the rice flour with 1/2 c water & knead into a dough the consistency of pie crust. Mold into 1 1/2" balls, then flatten with the palm of your hand to form patties 1/8" thick & 2" wide. Fill a large bowl half full with water & bring to a boil. Cook the rice cakes for 4 to 5 minutes or until they start to float. While still hot, coat each side of the cakes with the coconut-salt mixture. Place 1/4 to 1/2 ts of the mung beans into the centre of each cake. Fold the edges over & pinch closed to form a half circle. Dip each into the sesame seed-sugar mixture, coating both sides well. Serve hot or cold. They will keep in the refrigerator for 2 to 3 days.