To Cook
Steam diced yam, golden and purple sweet potato in a wok over high heat, until softened, about 20 minutes. Test with a sharp knife or toothpick. They should be very easy to prick through.
Use a large deep pot. Add 1 litre of boiling water with the rock and fine sugar. Bring it to boil. Add pandan leaves. Reduce heat to simmer for 10 min.
Pour in coconut cream. Once it boils again, drain up and discard the pandan leaves.
Add the sweet potatoes. The rock and fine sugar should dissolved completely.
Taste and add more sugar if needed. Served hot. Or let it cool down and chill in fridge if you like it served cold.
To Make Tapioca Flour Cubes
Sift tapioca flour if lumpy flour is found in it. Then, place tapioca flour and salt into a large mixing bowl. Slowly stir-in hot boiling water and combine well until mixture turns dough-like texture. When mixture is cooled, form it into dough on a well-floured table top.
Dust some flour on your palm and divide dough into 4 parts. Mix each portion with 3 different colouring prepared and leave one portion as ‘white‘ original colour (no colouring added).
Knead to combine well and until it becomes a non-stick dough. Then, roll and shape each portion out into long and squarish thin stripes. Thereafter, dice into small cubes.
Bring a pot of water to a boil over high heat. When boiled, reduce heat, and put in tapioca flour cubes to cook for about 30 min, or until all the cubes float up. Texture of cooked tapioca flour cubes should be chewy, bright in colour with a little translucent appearance.
Dish up and plunge cubes into a bowl of iced water for few seconds. Drain and remove cubes from iced water. Reserve for later.