Place green beans, water and pandan leaves in a pot. Cover and bring to a boil over high heat. Turn the heat down to low and simmer for 30 to 45 minutes until the beans are soft and start to break down.
Remove from heat and stir in dark brown sugar to taste. Serve hot, warm, at room temperature, or cold.
The beans have a tendency to boil over, so try to use a larger pot - for me, I used a 2-litre pot to cook the green bean soup. If you don't have a larger pot, place a ceramic spoon in the pot together with the rest of the ingredients and cook together. Do still keep a close eye on the pot and leave the lid ajar if necessary while simmering so that the soup doesn't boil over.
Desserts tend to taste less sweet when they are hot or cold, so depends on whether you are serving the soup hot, warm, room temperature or cold, the amount of sugar added will need to be adjusted.
Leftover soup can be frozen in popsicle moulds to make a tasty treat!