Boil raw mangoes in one and a half cups of water till tender. Peel them and extract mango pulp. Mix together mango pulp, ground mint-coriander-chilli paste, salt, black salt, roasted cumin powder and lemon juice.
Add five cups of water and mix well. For meetha pani add sweet tamarind chutney as per taste and mix. Chill in the refrigerator till use.
You can use a variety of fillings to fill the puris like sprouted moong or boondis mixed with potatoes etc. To make the sprouted moong filling,blanch moong sprouts (you can also use mixed sprouts) with a pinch of turmeric powder and salt.
Drain thoroughly and add red chilli powder and mix. For the boondi-potato filling, soak boondi in water for five minutes. Drain and squeeze lightly to remove excess water.
Mix it with cubes of boiled potatoes and season it with salt, chaat masala, red chilli powder and cumin powder.
Fill each puri with a little sprouted moong or boondi-potato mixture, then fill it up with the flavoured water and relish the pani puri.