Soak 1 cup of dried green peas overnight, then pressure cook them with 2 cups of water and a pinch of salt for 4-5 whistles until soft.
Heat 2 tablespoons of oil in a pan, add 1 chopped onion, 1 teaspoon of ginger-garlic paste, and sauté until the onion turns translucent.
Add 1 chopped tomato, 1/2 teaspoon of turmeric powder, 1 teaspoon of red chilli powder, 2 teaspoons of chaat masala, and salt to taste. Cook until the tomatoes are mushy.
Add the cooked peas to the tomato mixture, along with 1 cup of water. Mash some of the peas slightly to thicken the gravy. Simmer for 10 minutes.
Prepare the puris by rolling out small balls of whole wheat dough and deep frying them in hot oil until they puff up and turn golden brown.
To assemble the chaat, place 5-6 puris on a plate, crush them lightly, pour the hot peas gravy over them, and top with finely chopped onions, tomatoes, coriander leaves, sev, and dollops of tamarind chutney and green chutney as per taste.