2 tbsp extra black glutinous rice flour for dusting the ang koo´ mould
1 tbsp corn oil to brush the top of cooked or koo´
150g mung beans without skin (lok tau pean), soaked overnight and steamed for 30 minutes or until soft and blended until fine
1/4 tsp salt
1 tbsp oil
125g castor sugar
2 pandan leaves, knotted
For the filling: Put water, sugar and pandan leaves in a non-stick pan. Cook until the sugar has dissolved completely. Discard the pandan leaves and add the mashed mung beans and oil. Fry until the mixture turns dry and leaves the sides of the pan. Divide dough into round balls of 3334g each.
For the dough: Bring water, sugar, salt and pandan leaves to a boil to dissolve the sugar. Remove the pandan leaves. Put black glutinous rice flour, corn flour and wheat starch in a mixing bowl. Pour in the hot syrup and stir with a wooden spoon. Add in the mashed sweet potato and oil. Mix into a soft and smooth dough. Divide dough into portions of about 23g each. Wrap filling with a piece of dough and coat lightly with black glutinous rice flour.
Dust the ang koo mould lightly with a little glutinous rice flour and put in the wrapped dough. Press down, then knock out the or koo´.
Place the or koo´ on a lightly greased banana leaf (cut into round shape). Finish off with the rest of the dough. Steam the or koo´ over medium-high heat for 5-6 minutes. Open the lid and wipe the lid of the steamer to prevent water from dripping in.
Close the lid and continue to steam for another 810 minutes over medium heat.