To begin, rinse the glutinous rice thoroughly in cold water until the water runs clear. Soak the rice in water for at least 4 hours or overnight. This step is essential for achieving the perfect sticky texture.

Drain the soaked rice and transfer it to a steamer lined with cheesecloth or a fine sieve. Steam the rice over medium heat for about 25-30 minutes until tender and translucent. Make sure to cover the steamer to retain the steam.

While the rice is steaming, take a small saucepan and combine 1 cup of coconut milk, 1/2 cup sugar, and 1/4 teaspoon of salt. Stir over low heat until the sugar is fully dissolved. Be careful not to boil the mixture, just heat it until everything is well incorporated.

Once the rice is cooked, transfer it to a large bowl. Gradually pour the warm coconut milk mixture over the rice, gently stirring to ensure even distribution. Let the rice absorb the coconut milk for about 10-15 minutes. The rice should become creamy and sticky, but still retain its structure.

While the rice is absorbing the coconut milk, prepare the sweet coconut sauce. In a small saucepan, heat the remaining 1/4 cup of coconut milk with a pinch of salt. Bring to a gentle simmer and set aside. This sauce will be drizzled over the finished dish for an extra layer of flavour.

Prepare the mangoes by peeling them and slicing them thinly. The sweetness and ripeness of the mangoes are key to balancing the dish, so choose ones that are ripe but not overly soft.

To serve, place a portion of the sticky rice on each plate, shaping it into a neat mound. Arrange the mango slices next to the rice. Drizzle some of the sweetened coconut sauce over the rice for added creaminess.

For the finishing touch, sprinkle toasted sesame seeds or mung beans on top of the rice for a subtle crunch. Serve immediately while the rice is still warm and the mangoes are fresh. The contrast between the creamy, sweet rice and the refreshing mango slices makes this dish a beloved Thai dessert.