Rinse black sweet rice under cold water until water runs clear. Soak rice in water (enough to cover) overnight or at least 4 hours minimum. Drain water completely then add black sweet rice and 1.5 cups water to rice cooker then press cook button. If using regular sweet rice, use 1.25 cups of water.

In a medium pot, combine coconut milk, sugar, and salt. Cook over medium-low heat, stirring constantly, until sugar and salt dissolves but mixture is not boiling. Remove 1 cup of coconut milk and set aside. With remaining coconut milk, add cornstarch slurry and cook over low heat, stirring constantly, until sauce thickens. Turn off heat and set aside.

Once rice is cooked, let steam inside rice cooker or pot for 5 mins. Then transfer to a large bowl and pour 1 cup of warm coconut sauce over it. Mix well to incorporate then let sit for about 15 mins to allow rice to absorb the sauce.

While rice is resting, peel mangoes, slice into thin strips, and set aside.

Dip rice paper in cold water for a few seconds, shake off excess water, then lay flat on plate until softened. Sprinkle a few sesame seeds in the middle, add about 4-5 slices of mango, about ¼ cup of sticky rice. Fold the sides towards the center, then bottom towards center and roll to get a log shape. Repeat with remaining ingredients.

Serve summer rolls immediately with the coconut sauce.