Rinse the glutinous rice under cold water until the water runs clear. Soak the rice in water for at least 4 hours or overnight. Drain well.
If using a rice cooker: Combine the drained rice and 1 cup of water in the rice cooker pot. Cook using the white rice setting.
While the rice cooks, prepare the sweet coconut sauce: In a small saucepan, combine 1 can of coconut milk, 1 cup of sugar, and 1 teaspoon of salt. Heat over medium heat, stirring until the sugar and salt dissolve completely. Do not boil.
Once the rice is cooked, immediately transfer the hot rice to a large bowl. Pour about 3/4 of the warm sweet coconut sauce over the rice. Stir gently until the liquid is absorbed. Cover the bowl and let it steam for 20 minutes.
Prepare the topping sauce: In the same small saucepan, combine the remaining 1/4 cup of coconut milk, 1 tablespoon of sugar, and 1/4 teaspoon of salt. Heat gently until the sugar dissolves. Set aside.
Peel and slice the mangoes.
To serve, place a portion of the sweetened sticky rice on a plate. Arrange the mango slices next to the rice. Drizzle the reserved topping sauce over the rice and mango. Sprinkle with toasted sesame seeds if desired.
Notes
Use very ripe mangoes for the best flavor; Ataulfo or Honey mangoes work well.
For a vegan option, this recipe is naturally vegan.
For a gluten-free option, this recipe is naturally gluten-free as it uses rice.
If you do not have a rice cooker, steam the soaked rice for 25-30 minutes until tender.