To cook the sago: Bring a pot of boiling water, then add in sago and cook for 10 minutes under medium heat. Remove from heat and let it rest for 15 minutes. The sago will become transparent.
Put the sago under water, that can make it not stick together. Then drain well. Set aside.
Peel and cut the purple sweet potato into small pieces. Steam half the sweet potato for 10 minutes or fully cooked. Then use fork to mash it to puree.
Bring 500ml water to boil, add in the rest of the sweet potato. Cook for 10-15 minutes until softened.
Add in rock sugar, coconut cream and sweet potato puree. Mix well and cook for two minutes. Then add in sago and mix well. Enjoy!