Grind the coconut, one tsp of mustard seeds and green chilies by adding 3 tbsps of water into a smooth paste.
Now add this paste to the ⅔ cup of buttermilk.
Add salt and mix well.
Now in a tempering pan, heat the coconut oil.
When it is hot, add the remaining one tsp of mustard seeds and curry leaves.
When the mustard seeds splutter, add it to the buttermilk mix.
That's it. Instant Mor Kuzhambu is ready. :-)
Serve hot with rice and if you don't want turn on your stove for making curry, then try this oven roasted potatoes with rosemary or Indian style baked potato curry and pair it with the rice and kuzhambu.
Notes
As always adjust the salt and spice according to your preference and depending upon the sourness of the buttermilk.
If you need thin consistency, increase the buttermilk or add more water.
Instead of green chilies you can include 1 to 2 tsps of whole pepper and make it as pathiya mor kuzhambu.