Rinse and drain glutinous rice in tap water several times until water becomes clear, to remove starch. Transfer to a bowl and soak in enough water for at least an hour or overnight.
Drain the water and transfer the rice in a steamer basket lined with a cheese or muslin cloth. Add 4 pieces of pandan leaves. Place the steamer basket over the pot with boiling water. Steam for 15-20 minutes or until rice becomes translucent and cooked. Remove pandan leaves and transfer rice to a large bowl and fluff it several times using a spoon so they will not lump together. Cover and rest for 5 minutes.
Meanwhile, in a large pot or deep pan, combine coconut milk, sugar and salt. Bring to a gentle simmer over medium heat. Turn off the heat once it simmers and sugar is completely dissolved. Remove from the stove. Take ¼ cup of coconut cream and set aside for toppings.
Pour half of the remaining hot coconut milk to the bowl of still steaming hot rice and gently toss until well combined. Gradually add more of coconut milk to the rice and stir. Do it gently to prevent rice from becoming mushy. You might need to use all the remaining coconut milk or not, the target is to have a grainy but slightly wet and sticky porridge texture. Remember that the hot rice will continue to absorb the liquid as it cools down. Cover the bowl with plastic wrap so the top will not dry out.
Return the reserved ¼ cup of coconut cream to the saucepan and add the cornstarch slurry. Cook over low heat stirring constantly until it thickens a bit. Remove pan from heat and transfer the sauce to a bowl or milk pourer for serving later.
As the rice cools down, peel the mango/es. Cut the flesh from the pit on both sides and cut them in cubes or slices.
Assembly: Fill a small cup with sticky rice and invert it into a plate or bowl. Add slices of mangoes on the side. Pour some coconut cream sauce on top of the rice and mango slices or serve it in a saucer as a dip. Sprinkle with some roasted sesame seeds