Kaalan (Malayalam: കാളൻ [kaːɭan]) is a Keralite dish from South India, made of yoghurt, coconut and a raw fruit nendra kaaya or a tuber like the chena.
It is very thick, which distinguishes it from a similar curry known as pulisseri, and more sour than avial. For the same reason, kaalan can last longer when stored.  In many preparations, more pepper and/or chillies are added to make the kaalan spicy, in addition to its signature sour taste.
Kaalan is typically served as part of the Sadya.