A traditional rice cake made from glutinous rice flour and mixed with mashed sweet potato, filled with grated palm sugar, boiled and then coated with shredded coconut.
Place a steaming rack in a large wok and fill the wok with one third full of water and bring to a boil. Cover with wok lid and steam the sweet potato pieces on a large plate on medium to high heat for 25 to 30 minutes or until sweet potatoes are soft.
Remove and set aside in a large mixing bowl to cool until sweet potatoes are just warm. Mash the sweet potatoes with a potato masher or a fork and spoon.
Add all the glutinous rice flour, vanilla extract, salt and water into the mashed sweet potatoes, mix well and knead into a soft dough (Add more water if dough is too dry or more glutinous rice flour if dough is too wet).
Pinch and shape the dough into small balls about 3cm (1 inch) in diameters, make a well in the middle of each ball and fill with 1 teaspoon of grated palm sugar. Wrap the palm sugar with the dough and roll and form a smooth ball with your palms and place on a large plate. Repeat with the rest of the dough until finished.
Bring a medium pot half filled with water to rolling boil. Carefully drop about 10 balls into the pot and cook on medium heat. Once the balls float on the surface of the water, simmer for another 2 minutes.
Remove and drain the balls with a slotted spoon. Set aside on a large plate 1/2 inch apart. Make sure they do not stick together. Repeat and cook the balls in 4 to 5 batches.
Once the balls have cooled down slightly, immediately coat each of the balls evenly with desiccated coconut and serve warm.