In India, the humidity and heat have a way of making fresh curds/yogurt SO sour that it practically "speaks" - tilt the container even a little and evil little burping, bubbling noises happen on the surface. It's a heck of a struggle to keep the yogurt sweet and fresh. Refrigerating the curds helps, but it is not prevention, merely a postponement of the inevitable sourness. And when the inevitable happens, it is time to make mor kuzhambu with the curds.
Here in the UK, the problem is reversed... the yogurt/curds simply does not get sour - assuming, that is, that I've been able to get it to set in the first place. The buttermilk you get in the supermarket is not buttermilk as I knew it in India - it looks and tastes very much like plain set yogurt thinned down with a little water to make it of pouring consistency. Of sourness there is not even a hint.
So when I get the urge to make mor kuzhambu here, I have to use artificial means (1/4 tsp of tamarind paste, to be precise) to make the curds taste sour. Is anybody wondering WHY I bother, when I'm a self-confessed hater of sour curds? Well, the answer is that the sourness is necessary to make this recipe... because when it is tempered with the simply spiced coconut "masala", the sour curds/buttermilk is transformed into a thing of - well, perhaps not beauty, but definitely tastiness.
It's comfort food for South Indians like me, that's for sure. Team it with pan-roasted potatoes, vazhakkai (plantain) curry or cabbage/beans paruppu usili and you get the maximum comfort and pleasure from this simplest of preparations. At least I do.
Recipe for: Mor kuzhambu
4 cups sour buttermilk (or 2 cups plain Greek yogurt mixed with 3 cups water and 1/4 tsp tamarind paste to make a fairly thick buttermilk)
2 tbsp fresh grated coconut
5-6 green chillies (add as per taste)
1/2 tsp cumin seeds
1 tbsp rice flour
Salt to taste
2 tsp mustard seeds
4-5 curry leaves
pinch of asafoetida powder
2-3 dry red chillies (optional)
1 tsp oil
1 tsp chopped coriander leaves, for garnish
1. Grind the coconut along with the cumin seeds, green chillies and rice flour to a smooth paste, using a few tbsp of warm water.
2. Stir this paste, along with salt to taste, in the buttermilk until well mixed. Set aside.
3. In a pan, heat the oil, add the asafoetida, the mustard seeds and curry leaves (also the red chillies, if using), cover and let the seeds pop for 30 seconds or so.
4. Pour the buttermilk-coconut mixture into the pan and stir well. Bring to a simmer, stirring frequently, until the mor kuzhambu is heated through.
Tip: Be careful not to bring it to a boil or leave it on the stove for long, because the curd will very likely separate and make the whole thing look disgusting - although the taste will not be affected.