Rinse each pandan leaf thoroughly. Pandan is a little like leek in that they can hide a lot of dirt in between the leaves, especially towards the stem near the bottom.
Chop off the pale white stem area if that's included on the plant and discard, leaving only the dark green leaves.
Chop the leaves into small segments, about an inch long.
Add leaves to a high speed blender along with enough water to equal double the weight of the pandan leaves.
Blend on high speed until very smooth. (I use the Smoothie mode on my Blendtec which is perfect.)
Pour the juice a little at a time through a fine-mesh strainer into a container. Use a spatula or spoon to press down the pulp to fully squeeze out every drop of juice.