Grind mint leaves, coriander leaves with little water to form a smooth paste. Then add rest of ingredients until all blends well.Add 2 cups of water or as consistency required. Place in the fridge to chill or add some ice cubes for instant cooling.Soak tamarind and dates in boiling hot water. Alternatively you could boil the for 2-3 mins.Allow to cool remove the seeds of tamarind or dates. You could also use tamarind pulp and pitted dates for convenience.Now grind the pulp of tamarind and dates together with a cup of water until smooth.Take a pan add the puree of dates and tamarind. Add ½ cup water and mix all nicely.Also add jaggery powder and all spice powder, mix and simmer for 4-5 mins.Allow to thicken then switch off the gas. Place aside to cool.Mix all the spice powder with a spoon and place them aside. Once the ragda, moong sprouts and boiled potatoes are ready. Mix a teaspoon of this spice powder mix and adjust as per your taste. I don't have a pic for this one.Boil potatoes until cooked. Peel off their skin and chop them into small cubes. Take a mixing bowl and add the mix spice powder as required.Similarly boil the moong sprouts and strain excess water. Mix the spice powder as required. I don't have a pic for this one but you could see in the final pic.Soak chana overnight pressure cook until 3-4 whistles or they are cooked and tender.Take little oil in a pan, once hot add mustard seed.Once they crackle add hing and turmeric.Now add the boiled chana and also add water.Cook until chana gets slightly mush. Mash it further with the back of spoon and once the mixture is thick add the spice powder mix. Allow to cool down.Make a small hole in the top center of the puri with the help of spoon or finger.Add some ragda mixture, potato mixture or moong mixture. Top with some chopped onion. You could add the filling of your choice.Now pour spoonful of meethi chutney or add as per your preference.Immerse the puri in the spicy water and eat.Serve the pani puris chilled and immediately else they would become soggy.