Pandan chiffon cake is very popular in Malaysia and Singapore and the surrounding countries. It is made with the pandan plant (pandanus, or screw pine). The leaves have a sweet flavour and it is extensively used in cakes and savouries. The juice is also used as a green colouring. You can find pandan leaves in Asian supermarkets and they can be costly. I use pandan essence instead; this can be found in Asian supermarkets as well.