Wash the rice three times until the water runs clear, then soak in room-temperature water for at least 8 hours or up to 24 hours.

Drain the rice and prepare a steamer by lining it with parchment paper to prevent sticking. If using a metal or glass lid, wrap it in a clean kitchen cloth to absorb excess moisture so the rice doesn't get soggy.

Place the rice in the steamer and steam until the grains are translucent and chewy to the bite, about 25 to 30 minutes.

While the rice steams, heat the coconut milk, sugar, and salt in a large pan over medium-high heat. Bring to a boil for about 3 minutes, stirring every 30 seconds to ensure the sugar dissolves.

Lower the heat to medium and fold the steamed rice into the coconut milk. Cook for about 4 minutes, stirring until the rice has absorbed the liquid and thickened.

Transfer the rice to a bowl and let it rest for 5 minutes—this allows the starches to settle and the flavors to fully penetrate the grain.

In a clean pan, simmer the coconut milk and sugar for the sauce over medium-high heat. Once it boils, lower the heat to low.

Stir the cornstarch and water together in a small bowl to create a slurry. Whisk the slurry into the simmering sauce and stir for 1 minute until it thickens enough to coat a spoon.

Peel the mangoes and slice the flesh into long strips. Portion the warm rice onto plates, arrange the mango alongside, drizzle with the coconut sauce, and sprinkle with toasted sesame seeds.