Soak. Transfer the rice to a large bowl filled with water. Make sure the bowl is large enough to hold enough water to cover the rice. Allow the rice to soak for at least 1 hour or up to overnight.
Wrap up the rice in a cheesecloth. After the rice has been soaking for at least one hour, drain and rinse, then transfer to the center of a large cheesecloth. Allow it to drain. Then loosely wrap the rice in the cheesecloth (loose, yet secure enough that none of the grains can escape).
Prepare your steamer. I do not own a sticky rice steamer pot (which I expect is the same for many of you as well). I improvised and made my own by inverting a large mesh stainless steel steaming basket and placing it in a tall pot. The inverted basket creates a barrier between the boiling water at the bottom of the pot and the cheesecloth wrapped rice resting on top of the steamer basket. Since we're steaming the rice, the idea is to keep the rice from being submerged in water.
Steam. Add enough water to your pot so that it is filled by approximately 1-inch. Transfer the wrapped-up rice to the pot and place it on top of the steaming basket (making sure it doesn't fall to the side and into the water). Cover with a tight-fitting lid and bring water to a boil over high heat. Reduce heat to a simmer and allow the rice to steam for 15-20 minutes, or until grains become translucent.
Heat the coconut milk. As the rice steams, heat 1 can of coconut milk over medium heat. Stir often to prevent the coconut milk from burning or curdling. Add the sugar and salt, stirring continuously until dissolved. Set aside, keep warm.
Put it together. Transfer the steamed rice to a large bowl and mix with the sweetened coconut milk. Cover. Allow rice to rest for 5 minutes as it absorbs the coconut milk.
Prepare the coconut cream sauce. In a small saucepot, add the coconut cream (or milk) and sugar. Bring to a low boil, then reduce heat to low. Simmer until slightly thickened.
Serve. Transfer a scoop or warm coconut sticky rice to a small serving plate and serve with seasonal mango, coconut cream sauce, and a small sprinkle of sesame seeds, if desired.