Rinse rice until water runs clear; soak in cold water at least one hour.

Drain; steam in a bamboo steamer or regular steamer basket 20 to 25 minutes, until tender.

Meanwhile, heat coconut milk, sugar, and salt in a small saucepan over medium heat until sugar dissolves. Do not boil.

Transfer cooked rice to a bowl; stir in half the warm coconut mixture. Stand 15 minutes to absorb.

Serve with mango slices; drizzle with remaining coconut sauce and sprinkle with sesame seeds.