Mix the ragi flour with water to make a smooth lump-free slurry.
Heat ¾ cup water and bring it to a boil.
Add the slurry and cook on low heat, stirring continuously until it thickens.
Switch off the heat and allow it to cool completely.
Shape into balls and place them in a clay pot with 1½ cupswater. Cover and allow it to ferment overnight.
The next morning, mash the fermented ragi balls thoroughly in the same water until fully dissolved.
Whisk the curds well and add it to the fermented ragi mixture. Curds add a lovely refreshing flavour to the ambali. Churn well.
Now add salt, chilli-ginger paste, coriander leaves, and chopped onions if using.
Serve chilled or at room temperature.