Blend together the yogurt and water with a hand whisk. Add the salt and mix well.
Grind the coriander, curry leaves, garlic and chilli into a paste using a food processor.
Add it to the yogurt mixture. Mix well.
Add some ice cubes into two tall glasses.
Pour the chaas over the ice cubes and serve.
You can prepare the chaas and leave it in the fridge till its cold.
Try out the mint chilli garlic variety instead of the coriander.
I like to make extra coriander, garlic, curry leaves and chilli paste and store it in the freezer in a zip lock bag, patted down. Whenever I want to add it to the chaas, I snap the required amount and add it.
You can add more water if you like a thinner yogurt drink.