Soak peas: Soak white vatana overnight, then drain and rinse well.
Make spice slurry: Mix all dry spices with 2 tablespoon water in a small bowl.
Sauté aromatics: Turn Instant Pot to Sauté, add oil, then cumin seeds until they crackle. Add green chilies and ginger paste, sauté briefly.
Add spices and main ingredients: Add spice slurry, stir well. Add vatana and potatoes, mix to coat.
Pressure cook: Add 1 and a half cups water, close lid, pressure cook on High for 3 minutes. Natural release for 10 minutes.
Mash and finish: Mash potatoes lightly with ladle to thicken. Stir in cilantro.
Serve: Pour into bowls, top with onions, tomatoes, chutneys, sev, papdi, and cilantro. Serve hot.