Bring 2 cups of the water to a boil.
Add mung beans. Reduce to a simmer and cook for 20 minutes.
All of the water will have been absorbed by the beans.
Transfer the cooked beans with 1 1/2 cups of the coconut milk and process well in a food processor until very smooth.
Pass through a fine strainer/sieve into a pot.
Add the rest of the coconut milk and water with the sugar.
Bring to a simmer over medium heat and cook for about 10 minutes, until slightly thickened.
Serve warm, garnished with the sesame seeds