Prepare the rice:Soak the rice for 2 hours or longer, for a couple of hours or overnight. Rinse the soaked rice with water.
Steam the rice for about 20 minutes, it’s ready when it’s soft and translucent, but should have just a slight bite to it.
How to steam the rice:Use a steamer or this simple method requiring 2 large pots and a fine-mesh strainer or a splash guard. Pour boiling water into a large pot, put a splash guard or a fine mesh-strainer on top (it shouldn’t touch the water surface). Place the soaked rice on it, in an even layer, cover with a second pot or a lid (large enough to cover the rice without touching it). Fine mesh strainer will only work with small amounts of rice, you need to make a hollow in the rice portion, its layer should have an even thickness on every side of the strainer (or the rice won‘t cook evenly). Cook over medium heat until soft. Larger amounts of rice, e.g. 2 cups, should be stirred once during steaming. If you're using a splash guard, just place the rice in an even layer on it. Soak the rice in coconut milk: Transfer the rice into a medium bowl, smooth its surface with the back of a spoon.
If you're using palm sugar in blocks, you need to crush it into smaller pieces. Put the 1 block of sugar in a zip lock bag and pound it with a meat mallet. You will need a 3/4 of one, 3-inch (7cm) block for this recipe, you can also add more if you wish.
After opening the coconut milk can, mix thoroughly its content - thick and thin part. Pour coconut milk into a small pot (1 and ¼ cup), add sugar and salt, cook over medium heat (but don’t let it boil) until the sugar dissolves.
Add ¾ cup coconut milk with sugar to the rice, leave ½ cup in the pot.
Cover the bowl with plastic foil, let stand for 30 minutes, or until the rice absorbs the liquid.
Make the coconut sauce: add the rice flour to the remaining coconut milk in the pot, cook on medium heat for a couple of minutes, until thickened. Prepare the mango: peel, remove the pit and cut into slices.
Serve: place a portion of rice on a small plate, then mango slices on top, pour the coconut sauce over and sprinkle with shredded coconut. Serve warm.