Bring to boil in a pot or wok. Add a liberal pinch of salt and a couple of drops of cooking oil. Whilst water is boiling rapidly, add Choy Sum and blanch it until the leaves turn dark green, indicating that it is cooked. Remove and drain. Arrange Choy Sum on a plate.
Heat cooking oil in wok and fry the sweet tau kee for 1 minute on both sides on medium high heat. Once done, push the sweet tau kee to one side and add garlic to remaining oil. Saute till aromatic.
Then, push back the sweet tau kee to the garlic and add 200 ml water. Bring gravy to boil and add seasoning to taste. Gradually add potato starch to thicken gravy to your preferred consistency. Then, pour gravy with sweet tau kee and garlic over the pre-arranged Choy Sum.