In a large bowl, wash the glutenous rice with tap water. Discard the water and repeat about three times or until the water runs clear.
In a bowl, add the glutinous rice and enough boiling water to completely submerse the rice. Stir the rice in the boiling water then let it sit for 5 minutes. Once done, stir again and strain.
Place the rice back into the bowl and completely submerse the rice in plenty of boiling water. Let it sit for 25 minutes covered with cling wrap and stir the rice once at 15 minutes.
After 25 minutes, strain the rice. Put the strainer under a tap with warm - hot water and use your fingers to move the rice around in the strainer until the gooey texture is gone.
Add the sticky rice and 180 ml of boiled water to the casserole dish and pat the rice down so it is flat. Cover with a lid or cling film and microwave for 7 minutes.
After 7 minutes, take out the rice and fluff it up gently with a pair of chopsticks or spoon. Place the lid back on and put it back in the microwave for a further 4 minutes.
Take out of the microwave and taste a few grains of the sticky rice for texture.
If the rice is is too mushy, then leave the lid off and cook it for a further 2 minutes in the microwave. If there are a few hard bits, then add a 1 - 2 tbsp of water first before putting in the microwave. Otherwise, put the lid back on and cook for 2 minutes.
Prepare the steamer and make sure it is hot before adding the rice.
Add a cheesecloth or chux cloth at the bottom of the steamer bowl to avoid rice falling through the holes. Add the sticky rice to the steamer and cook for roughly 18 minutes. (check the rice before taking it out)
Add all the coconut mixture into a small pot and stir until combined. Add the pandan leaf (if using) and let it simmer on low until needed. I
Once the rice is done, put the rice in a bowl and add the coconut mixture. Stir it in with a wooden spoon and let it sit covered for 15 minutes.
In a pot on medium heat, add the coconut cream and salt. Stir until combined.
In a small bowl, mix the rice / corn flour with water. Add it to the sauce and stir in well. Take it off the heat once the sauce starts thickening.
Cut mangoes into chunks, wedges or whatever your preference.
Divide the rice and the mango chunks into bowls.
Pour a few teaspoons of the sauce over the top and garnish with sesame seeds.