Bring the water to a boil in a small saucepan. Quickly stir in the soaked rice and add the 2 tablespoons sugar. Let boil for 2 minutes, and then reduce the heat to very low. Cover and simmer only until water has evaporated and rice is tender, 8 to 10 minutes. Remove pan from heat and let sit for 20 minutes. Uncover and fluff rice with a fork or chopsticks. Set aside.
In another small saucepan, combine the coconut milk, vanilla, salt, and the 1/4 cup sugar and bring to a boil. In a small bowl, mix the cornstarch with 1/3 cup water and stir until well dissolved. While the coconut sauce is simmering, slowly drizzle in the cornstarch mixture and stir until sauce is just thick enough to coat a spoon. Remove from heat and set aside.
To serve, place a small, neat mound of sticky rice, about 1/2 cup in the center of each serving plate, Surround each mound of rice with mango slices. Drizzle 2 to 3 tablespoons of the coconut sauce over each mound and sprinkle with sesame seeds.
source from: vietnameseportal