add oil in it quickly add curry leaves slit green chilli dry red chillies and mustard seeds in it once they crackle turn off the flame and pour it over the diluted curd in the jarstep 3you can use a large spoon to stir and mix the tempering now you just have to add the ice cubes in the prepared chaas and sprinkle some chaat masala over it along with chopped coriander leaves stir once again and serve it chilledpreservation tip buttermilk can last longer than most dairy products and so you need not worry about it you can consume it after 34 days too just make sure that you store in airtight container else it might get sourer in taste