To prepare the pandan glutinous rice balls: Blend or process pandan leaves and water in a food processor until fine.
Strain the pandan juice through a fine sieve to get 120ml pandan juice.
Combine glutinous rice flour, rice flour, sugar and pandan juice in a mixing bowl. Stir to mix until a dough is formed. Divide dough into small portions and roll into balls. Put them in boiling water and once they float dish out and soak in cold water for about 10 minutes. Dish out and drain.
To prepare pandan-potato glutinous rice balls: Put glutinous rice flour, sugar and mashed sweet potatoes in a bowl. Add water and mix to a soft and smooth dough. Pinch into small portions and roll into balls. Boil in a pot of boiling water until balls float. Dish out and soak in cold water for a while. Dish out and drain.
Cook barley, gingko nuts, rock sugar, pandan leaves and water for about 30 minutes or until barley is cooked through. Discard pandan leaves. Scoop out barley into bowls, add glutinous rice balls and serve at once.