Begin by rinsing 1 cup of sticky rice under cold running water until the water runs clear. Then, soak the rice in enough cold water for at least 1 hour or overnight for an even softer chewiness. Once soaked, drain the rice and set it aside.

In a large pot, add water and bring it to a steady boil. Place the soaked and drained sticky rice in a heatproof bowl or a bamboo steamer lined with cheesecloth. Steam the rice over medium-high heat for 20-25 minutes, or until it's tender and sticky.

While the sticky rice steams, combine 1 can of full-fat coconut milk, 1/3 cup of sugar, and a pinch of salt in a medium saucepan over low heat. Stir gently until the sugar completely dissolves, taking care not to boil it.

Once the sticky rice is fully steamed, transfer it to a large mixing bowl. Pour about 1 cup of the warm coconut sauce over the rice, and gently fold it in to ensure even distribution. Let the rice sit for about 10 minutes to absorb the flavors.

To serve your mango sticky rice, scoop portions onto individual plates or bowls. Top with thinly sliced ripe mangoes, drizzling more coconut sauce over the top.