Soak the rice in a bowl of water for 3 hours. Drain then spread the rice in a steamer basket lined with muslin.
Fill a wok or a steamer pan with water and bring to the boil. Set the steamer over the water and steam on a medium heat for 20–25 minutes or until the rice swells.
Mix the coconut milk, measured water and sugar and salt in a small saucepan until smooth.
Spoon the hot rice into a bowl and mix it with the coconut milk mixture. Cover and leave to rest for 10 minutes.
Mix the coconut milk, flour and salt together for the coconut cream topping and gently heat in a saucepan for 2–3 minutes.
Peel the mangoes, cut into small slices and arrange on each plate. Serve with the sticky rice and drizzle with the topping, if liked.