Rinse the sticky rice under cold water until the water runs clear. Soak in water for at least 1 hour, or ideally overnight.

Drain the soaked rice and place it in a heatproof bowl. Steam for 20 to 25 minutes until translucent and tender.

In a saucepan, combine coconut milk, sugar, and salt over medium heat. Stir until sugar dissolves.

To thicken the sauce, dissolve cornstarch in water and stir into the coconut mixture, cooking until thickened.

Fluff the sticky rice and combine with 1 cup of the warm coconut sauce. Allow to rest for 10 minutes.

Peel and slice the ripe mangoes into thin pieces.

To serve, scoop sticky rice into bowls, place sliced mango on the side, drizzle with additional coconut sauce, and top with sesame seeds if desired.