1. Place sugar and 1¼ cups water into a saucepan and bring to a boil. Lower the heat and cook till the sugar is completely dissolved. Set aside.
2. Place tapioca flour and plain flour into a large heat-proof bowl. Add the pandan juice, coconut milk and remaining ¾ cup water. Whisk till smooth.
3. Stir in the syrup mixture, lye water and pandan essence. Whisk till smooth.
4. Fill a large saucepan halfway up with water and put it on the stove, over medium-high heat. Place the bowl of batter atop the mouth of the saucepan, ensuring the bottom of the bowl doesn’t touch the water. Stir with a whisk constantly until the mixture thickens to the texture of pudding, about 10 minutes.
5. Lightly oil the bottom and sides of a 20cm x 20cm baking tray. Pour the mixture into the tray and steam in a wok over medium heat for 30 minutes till set — when you use your finger to lightly press the top of the kueh, it should offer the barest of resistance.
6. Set aside to cool at room temp completely before refrigerating for at least 4 hours to set.
7. In the meantime, place grated coconut in a tray and steam for 8 minutes. Remove from the heat and stir in the salt.
8. To serve, slice the kueh into cubes and toss with the steamed grated coconut. You can make this kueh and steam the grated coconut up to two days in advance and refrigerate separately, wrapped. Cut and serve it cold.