Sago is artificial rice with loose texture. Don't soak it in cold water before cooking. You can soak it in hot water for a while, so that the appearance of sago is half-cooked because the temperature is enough, so that sago can keep its original shape during later cooking.

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Sago is a kind of edible sago starch, which is made from the trunk and stem of palm tree (Metroxylon sp) through mechanical treatment, soaking, precipitation and drying. The most traditional starch is extracted from the pith of sago coconut tree (also known as sago, Saiya skirt) and then processed by hand.

Sago is produced in Malay archipelago. Sago is white and flawless, and is called the West Valley of Zhu Zhen. It is white, slippery and nutritious. The general population can eat it. It is suitable for people with physical weakness, postpartum recovery, dyspepsia, mental fatigue, lung qi deficiency, tuberculosis, lung flaccidity and cough, and diabetic patients to fast.

References:

Baidu encyclopedia-sago, CCTV food network-red bean milk sago dew