Yogurt: I used medium consistency yogurt, so added 1/2 cup of water to dilute it. The yogurt should be neither too thick not too runny. This recipe is for 2 and 1/2 cups of buttermilk.
To give a simple tadka/seasoning, using only mustard, curry leaves, red chillies and chilly powder.
You can also add the seasoning to oil before adding coconut paste. But if you want the looks, especially when you are having guest over, add the seasoning in the end.