Rinse glutinous rice under cold water until water runs clear. Drain well.
In a saucepan, combine coconut milk, sugar, and salt. Heat over medium heat until sugar is dissolved and mixture is warm, but not boiling.
Add drained glutinous rice to the saucepan. Stir well to combine.
Reduce heat to low, cover, and simmer for 15-20 minutes, or until rice is tender and liquid is absorbed. Stir occasionally to prevent sticking.
Remove from heat and let rest for 10 minutes, covered.
To serve, scoop sticky rice onto plates. Arrange sliced mangoes alongside or on top of the rice.
Sprinkle with toasted sesame seeds if desired.