Put water, sugar and pandan leaves in a saucepan and bring to a boil over medium heat.
Add dissolved agar-agar and boil for 12?15 minutes, stirring frequently until sugar and agar-agar have dissolved completely. Discard pandan leaves.
Stir in coconut milk and bring to a boil, then remove from heat.
Pour the jelly mixture straight into a 23cm square tin.
Add the cendol and stir lightly to mix. Leave aside to cool completely.
Chill the jelly well in the refrigerator before cutting into serving pieces.