In a colander or mesh strainer, rinse the rice until the water runs clear. Then, place in a small bowl and cover with water. Let sit covered on the counter for 8-12 hours, or overnight.
Prepare your steaming station. Add 2 cups of water to the bottom of a large pot. Place the steamer basket inside and line it with the cheesecloth.
Drain the rice and sprinkle it evenly over the cheesecloth. Bring water to a boil. Cover and let steam for 20 minutes. You may need to add more water as it cooks. Give the rice a little stir at the 20 minute mark, then continue to steam until rice is translucent, sticky, and chewy. For my rice it was about 25 more minutes for a total of 45 minutes.
Remove rice from steamer and set aside.
Open the can of coconut milk and scoop the solids off the top. Set aside. Pour the remaining liquid into a small saucepan. Add 1/3 cup sugar and 1/2 teaspoon of salt. Heat over medium heat until sugar dissolves.
Combine coconut sauce and rice and stir. Cover and refrigerate until the rice absorbs most of the liquid.
Once the rice is ready, make the coconut cream sauce. Place solids from the can of coconut milk into a pot. Add 3 Tablespoons of sugar and a pinch of salt. Bring to a boil over medium heat. Boil for 2 minutes and then remove from heat.
To assemble, layer rice, sliced mango, coconut cream sauce, and toasted sesame seeds.