Updated on 15th January, 2008: I was asked what the difference between a Pulissery and a Kaalan was. It seemed appropriate to include my answer in this post.
Both Pulissery and Kaalan are dishes where the cumin seeds, green chillies and grated coconut are ground to a paste and cooked with yogurt to form a gravy.
Pulissery is made using one of these vegetables, usually vellirika ( a sort of cucumber), elavan (ash gourd), raw mangoes and sometimes a combination of elavan and raw mango, or fruits like mango, plantains or pineapple. Pulissery is thinner in consistency compared to Kaalan.
Kaalan is usually made with vegetables like chena (elephant yam) or vazhakka (raw plantain) and sometimes with ripe mango. Kaalan is much thicker in consistency and also has black pepper added to it.
In the age before refrigeration, sour yogurt was usually boiled/ cooked with salt, turmeric powder and crushed black pepper till the water evaporated leaving behind a thick mass. This was called “Kurukku Kaalan”. This keeps for a very long time. Then whenever, Kaalan was to be made, the vegetables would be cooked in a little water and then the above mentioned coconut paste and some part of the Kurukku Kaalan would be added to make a Kaalan, which was then tempered with mustard and fenugreek seeds and curry leaves in coconut oil. If Kaalan is made with ripe mangoes, then the crushed pepper is not added.
In many communities in Kerala, Kaalan is an important part of festive fare, where it is served with rice before the sambhar is served. If anyone has any other information about this I would be glad to hear from you.