Garnish
Heat a medium, heavy-bottomed pan over medium-high heat.
Once hot, heat the oil and add the cumin seeds and onion.
Saute for 7-8 minutes, until golden.
If the mixture gets dry, deglaze with 1-2 Tablespoons of water.
Add the garlic, ginger, and green chili pepper and saute for another 2-3 minutes.
Deglaze the pan with a Tablespoon of water (if needed), and add all the spice powders.
Give it a few stirs to roast the spices.
Add the tomatoes.
Saute for 2-3 minutes more.
Mix in the chickpeas, potatoes, baking powder (optional), salt and water.
Raise heat to high to bring to boil, then reduce heat to medium, cover and let cook for 25-30 minutes, until the chickpeas and potatoes are very tender.
Uncover and raise the heat to high.
Use a wooden spatula to slightly crush the chickpeas.
Saute for another 2-3 minutes to desired consistency.
Taste and adjust salt and seasoning.
Turn off the heat and add the garam masala (or chaat masala), lemon juice, and cilantro leaves.
Sprinkle with julienned ginger and black pepper, if desired.