Wash the coriander and mint leaves very well. Make sure there are no traces of dirt.
Now add the green chillies, black salt and lemon juice to the mixer grinder. Grind roughly.
Add a cube of ice, coriander and mint leaves and now grind to a smooth paste. Ice, salt and lemon will all help to maintain the green colour.
Take a small portion of this paste and add it to a glass of water. Mix and taste.
Check for salt and lemon, adjust as per your taste.
Take a silicone tray and fill it up with the paste. Tap the tray and place in the freezer. Once frozen, remove in an airtight container.
To make the water, add one cube of paste in a glass of 250 ml water. Add a pinch each of roasted cumin powder, asafortida ( optional ) and chaat masala. Stir well and drink it as it is or serve with crisp pooris stuffed with boiled potato and chickpeas.