Rinse the sticky rice in cold water several times until the water runs mostly clear.

Soak the rinsed rice in water for at least 1 hour or overnight for best results.

Drain the soaked rice using a fine-mesh strainer or colander.

Steam the drained rice over boiling water for 20 to 25 minutes, or until tender and sticky.

While the rice is steaming, pour the coconut milk into a small saucepan.

Add the sugar and salt to the coconut milk and warm over medium heat, stirring until the sugar dissolves.

Do not boil the coconut milk mixture; heat it just until it is hot and smooth.

When the sticky rice is done cooking, place it in a large mixing bowl.

Pour about three-quarters of the warm coconut milk mixture over the rice.

Gently stir to combine, then cover the bowl and let the rice absorb the coconut milk for about 20 minutes.

Reserve the remaining coconut milk sauce for serving.

Peel the mangos and slice them thinly.

To serve, scoop a portion of sticky rice onto a plate.

Arrange mango slices next to the rice.

Drizzle the reserved coconut sauce over the rice and mangos.

Sprinkle with toasted sesame seeds if using.

Serve warm or at room temperature.