Brush bottom and sides of a 5 x 8 baking dish with coconut oil or melted butter. Set aside.
In a wide, non-stick pan over medium heat, combine 4 cups of the coconut milk, 1 cup of the brown sugar, and salt. Bring to a simmer, stirring until sugar is dissolved.
If using, tie a pandan leaf into a knot and add to coconut milk-sugar mixture.
Add rice and cook, stirring occasionally, for about 20 to 25 minutes or most of the liquid is absorbed. Remove pandan leaf and discard.
Add water in 1/4 cup increments and continue to cook, stirring regularly, for about 25 to 30 minutes or until rice is fully cooked and the mixture is very thick and sticky.
Meanwhile, In a non-stick pan over medium heat, combine the remaining 1 cup coconut milk and 3/4 cup brown sugar. Cook, stirring occasionally, until very thick yet spreadable.
Transfer cooked rice into the prepared baking dish and flatten evenly.
Spoon coconut caramel topping over rice and spread across the surface to completely cover.
Bake in a 350 F oven for about 15 to 25 minutes or until topping is firm. Increase temp to 375 F and continue to bake for another 15 to 20 minutes or until topping is golden.
Remove from oven and allow to cool before slicing.