1. Grind together coriander leaves, mint leaves, green chillies, ginger and cumin seeds with little water to a fine paste.
2. Strain this mixture along with water into a large vessel.
3. Add salt, rock salt, red chilli powder and lemon juice.
4. Mix well. Refrigerate the pani.

To Serve:

1. Soak the boondi in 1 cup water for 10 minutes.
2. Squeeze out the water completely from the boondi.
3. Gently mix the boiled potatoes, boondi, salt and red chilli powder together.
4. Place about 6 purees in a plate.
5. Make a hole in the centre of each puree.
6. Put a tbsp of the potato boondi mixture in each puri.
7. Top it with ½ a tbsp of sweet date chutney and dip into pani.
8. Serve immediately.