Take a boiling pot or a pressure cooker and put the potatoes to boil.
In the meantime, chop the onions, and green chilis.
Slightly mash the white or yellow peas (boiled).
Next, when the potatoes are cooked to perfection, take them off the flame and let them cool completely.
Peel the potatoes when cold.
Transfer them into a large mixing bowl and mash them. It is okay to have a few lumps as this will increase the texture.
To the mashed potatoes, add cumin powder, coriander powder, fennel seed powder, chaat masala, salt to taste, black salt to taste, and the already prepared tamarind water.
Mix them well and then add in the chopped onion, green chilis, coriander leaves, and the white or yellow peas (slightly mashed).
Combine all the ingredients nicely and take a taste test. Add if anything is needed.