To make the moong sprout filling combine all the ingredients in a bowl, toss to mix well and set aside. To make paani grind coriander leaves, mint leaves and green chillies to a paste using water as required. Transfer coriander and mint paste into a large bowl, add paani puri masala, dry mango powder, black salt, salt, cumin powder and lemon juice and stir to mix well. Add six cups of water to the above mixture.
Stir to mix well and put to chill in the refrigerator. While serving add boondi to the prepared paani and stir. Take a puri, break a little of the crust, fill it up with a little moong and potato filling followed by a half a tablespoon of sweet date and tamarind chutney. Dip the puri in the prepared paani and serve immediately. Similarly prepare the remaining puris and serve.