Combine all the ingredients except the yogurt in a food processor or a blender and turn it into a coarse paste.
Add this to the whisked yogurt in a large jug, and adjust the consistency with cold water.
Pour into individual serving glasses and top with ice cubes and a sprinkle of cumin powder and/or chopped coriander leaves.
Notes
Depending on your personal preference, you can keep the spiced Indian buttermilk thick or watery.
You can also choose to substitute the regular salt with black salt for some added flavor. If you don't have either of these, you can use pink Himalayan salt as an alternative.
You can also use your blender to make the Chaas if you want to.