Wash glutinous rice, soak overnight (about 12 hours), drain and wash until clean. Drain and discard water.
Add pandan leaves if desired, then steam or cook the rice for approximately 45-50 minutes, stirring every 5 minutes with a spoon until it is cooked.
Remove the pandan leaves (if used) and transfer the rice to a big wok pan.
While the rice is cooking, place granulated sugar, brown sugar, and water into a pot. Stir over low heat until sugar is dissolved and everything is evenly mixed.
Add coconut milk, bring to a boil and stir until slightly thickened. Adjust sugar to taste.
Add mixture to glutinous rice and stir until everything is evenly mixed.
Pour mixture into the pan. Cover with plastic and hand-press gently to keep things uniform and dense in the pan.
Cut into diamond-shaped pieces. Cake is ready to be served.