While the rice is cooking simultaneously make the coconut sauce. In a small saucepan over medium low heat, add entire can of coconut cream. Gently stir and bring up to a gentle simmer.
Once the coconut milk is at a gentle simmer, add the sugar and salt. Stir well to dissolve, then adjust heat to the lowest setting. At this point you want to taste the sauce. If you prefer a sweeter sauce you can add more sugar. Now reserve ¼ cup of the coconut milk to save for drizzling on top.
When the rice is done cooking, immediately add it to the warm coconut milk. Doing so while it's still warm will allow the rice to soak up the coconut milk. Add it in batches and stir in between to incorporate. If serving right away, then remove from heat and allow to cool for about 15 minutes. If serving in about an hour, then keep it on the stove on the very lowest heat setting and stir periodically.
To serve, add rice to a plate or bowl, top with cold sliced or cubed mango, and drizzle with reserve coconut sauce. You can also garnish with toasted sesame seeds of mung beans if you like.
If serving the next day, store sweet coconut rice in the refrigerator and reheat in the microwave with a damp paper towel on top.Reserved coconut milk also needs to be stored in the fridge.