Grind everything into a blender with water until smooth paste is formed. Place it aside.Boil tamarind or dates in water for 3-4 mins. Allow to cool and remove if any seed.Grind them with a cup of water until smooth.Take a pan and add the puree.Add ½ cup water and mix nicely.Also add jaggery powder, spice powder and salt.Mix and simmer for 4-5 mins, allow to thicken.Switch off the gas and allow to cool.Firstly boil the potatoes until tender and cooked. Peel and chop them finely. Mix some chat masala and black salt into it and place aside.Mix yogurt with little chat masala,sugar, black salt and coriander powder. Beat the yogurt nicely and allow to chill for an hour before serving.Keep the sweet chutney, spicy chutney, spices and herbs ready.Take puffed pooris and place them on the serving dish. Now make a small hole into the puris to make space for the filling. I cracked a hole in the pooris through the back of a spoon.Now stuff each poori with spoonful of potatoes.Top the stuffing with spicy and sweet chutney as your preference.Add spoonful of chilled yogurt until it almost fills the puri.Sprinkle chat masala, roasted cumin powder, black salt and some raw mangoes.Time to sprinkle some nylon sev and squeeze some lime juice over them.Finally add chopped coriander leaves and red chili powder.Serve the dahi batata puri immediately and eat them before it turns soggy.