Soak and prepare the rice: Rinse the sticky rice thoroughly under cold water until the water runs mostly clear. This helps remove excess starch so the rice doesn’t become overly gummy. Soak the rice in clean water for at least 3–4 hours, or overnight for best texture. After soaking, drain it completely before cooking.
Steam the rice: Place the soaked rice into a steamer lined with cheesecloth or a clean cloth. Steam over medium heat for about 20–25 minutes, or until the rice becomes soft, tender, and slightly translucent. Halfway through steaming, gently flip or stir the rice once so it cooks evenly.
Make the coconut sauce: While the rice is steaming, pour coconut milk into a saucepan over low heat. Add sugar and salt, stirring slowly until everything fully dissolves. Do not let it boil too hard—just gently heat it so it stays creamy and smooth. If you want extra aroma, add vanilla extract at this stage.
Combine rice and coconut milk: Once the sticky rice is cooked, transfer it into a large bowl while it is still hot. Immediately pour most of the warm coconut milk mixture over the rice. Mix gently but thoroughly so every grain absorbs the sweet coconut flavor. Cover and let it sit for 20–30 minutes so the rice fully soaks up the sauce and becomes rich and creamy.
Prepare thick coconut topping (optional): Take the remaining coconut sauce and simmer it on low heat. If you prefer a thicker, more dessert-style drizzle, stir in the cornstarch slurry and cook for 2–3 minutes until slightly thickened and glossy. Remove from heat and set aside.
Slice the mangoes: Peel the ripe mangoes carefully and slice them into thin, even pieces. Make sure the mangoes are sweet, soft, and fragrant, as this balances the creamy rice perfectly.
Assemble the dish: Spoon a generous portion of coconut sticky rice onto a plate. Arrange fresh mango slices beside it in a fan shape or neat stack. Drizzle the thick coconut sauce over the top and finish with toasted sesame seeds or mung beans for a light crunch. Let it rest briefly before serving so the flavors settle, then serve slightly warm or at room temperature for the best taste.
