First Put the rice in a heatproof bowl and steam in a steamer, over medium heat, for about 20 minutes (based on one half cup of rice). The rice should be cooked through with no hard, raw bits in the middle of the grains. You can also cook the sticky rice without a steamer, using the splatter guard method.
Second Turn off the heat and let the rice stay in the steamer, with the lid on, while you prepare the coconut milk.
Third In a heatproof bowl, heat the coconut milk, sugar, and salt in the microwave on high for 2 minutes. The sugar should completely dissolve and the mixture should be very hot.
Next Take the sticky rice out of the steamer. Pour the hot coconut mixture on top of the rice and gently stir. (It may look like your rice is drowned in coconut water, but the liquid will all be absorbed.) Cover the bowl tightly with plastic wrap and let the mixture stand at room temperature, undisturbed, for half an hour.
Next The coconut sticky rice is to be served at room temperature along with fresh mango. The sesame seeds are optional.
Lastly The rice can be refrigerated and reheated in the microwave, but the texture of reheated sticky rice isn’t as good as it is when freshly made. Freezing sticky rice is not recommended.