Cut sweet potatoes into 1-inch cubes. Steam until cooked and soft, about 10 minutes.
Transfer sweet potatoes to a mixing bowl. Mash until smooth, then add in glutinous rice flour, salt, vanilla extract, and water. Mix until combined and dough is pliable. If your dough is too sticky, add in a bit more glutinous rice flour and mix until you have a "rollable" dough.
Bring a pot of water to a boil. Meanwhile, pinch off about 1 tbsp of the dough and roll into a ball. It should be approximately 1 inch in diameter.
Make a hole in the middle of the ball. Place ⅓ tsp of palm sugar into the hole, then close the dough around the sugar filling. When the sugar is nicely tucked inside, roll the ball again in your palms until a smooth ball is formed. Repeat with remaining dough.
Slowly place the dough balls in the pot of boiling water. Do not overcrowd. Meanwhile, place the desiccated coconut in a separate plate or bowl. When the balls float to surface, strain and set aside.
Roll the dough balls on a plate of freshly grated coconut until coated. Serve immediately. ENJOY!