You could do the preparation ahead of time. Boil Matar - Soak dried matar overnight or in warm water for 4-6 hours. Boil with salt in instant pot or pressue cooker until softened but not mushy. Boil Potatoes - Boil potatoes. Let cool slightly, peel them and using a sharp knife, cut into small cubes.
Make tamarind chutney if using homemade.
Finely chop onions, green chillies, cilantro and keep ready.
Make Potato Mixture
In a bowl, add the boiled potatoes, matar, chopped onions, green chillies, chaat masala, salt. Mix well.
Mix Yogurt
In another bowl, mix together dahi with sugar,red chilli powder, coated cumin powder, kala namak and salt. Add 2-4 tablespoons water if needed to adjust the consistency of yogurt mixture.Taste and adjust seasonings as per your liking.
Stuff Puris & Assemble The Chaat
Layer puri in a large plate/platter. Poke a hole in the middle of each puri using your finger. Make as large a hole as you can making sure that the puri stays intact.
Now you have to work fast. Stuff around 2 teaspoon potato mixture inside each puri. Spoon about 1 tablespoon dahi next.
Add about 1 teaspoon tamarind chutney to each puri.
Next add the chopped onions, green chillies, cilantro inside each puri for added kick and crunch.
Sprinkle the dahi puri chaat plate with pomegranate arils, generous amount of spices like roasted cumin powder, red chili powder, and chaat masala.
Add bhujia and sev on top. Serve immediately!
Notes
Add layers of flavors - Instead of just using boiled potatoes, make a spiced mixture of potatoes, matar, green chillies, cilantro, red onions and chaat masala. Make a spiced sweet yogurt mixture instead of just salted or sweet yogurt. You get the idea?
Don't use sour dahi- Make sure that the yougurt you are using is thick and not too sour. Else, combined with tamarind and chaat masala, these dahi puri will be too sour.
Avoid overstuffing - I know we all are tempted to load up our chaat, however overstuffing will hurt here since it will make the puris soggy sooner.
Serve immediately- Dahi Puri chaat is best served immediately after assembling to preserve the crispness of puris.
Texture is the key- Add texture and bite to dahi puri by topping the stuffed puris with chopped red onions, cilantro, pomegranate arils and sev/bhujia. The more texture you add, the better the taste.
Avoid drizzling extra wet ingredients like chutney or yogurt once you have the assembled the chaat plate. Makes them soggy quickly. Consider adding spices, sev, herbs, onions etc that enhance the look of chaat without making it mushy.
Variations
Make Vegan Dahi Puri - Simply use plant based yogurt. All other components in this recipe are vegan friendly.