Cook the soaked chickpeas covered by 1 1/2 inches of water with 2 tsp kosher salt in a pressure cooker (20 mins) or in rapidly simmering water (1 to 1 1/2 hours) until tender.
Meanwhile, heat 1/3 cup oil in a large stockpot (your biggest) over medium heat. Add onions and cook until very soft and deeply golden, about 30 minutes, reducing the heat to low if they start to brown too quickly.
Push onions to one side of the pot and add the remaining teaspoon of oil the space you made. Add the cumin seeds to the oil and increase heat to medium. When cumin is toasty (1-2 minutes), stir back into the onions along with jalapeño, ginger and garlic.
When garlic smells fragrant (another minute or so), stir in garam masala, cinnamon and salt to coat other ingredients, then add tomato. Cook the tomatoes down for about 5 minutes (you should see the oil bubbling up to the surface).
Stir in the potatoes, cooked chickpeas and water. If mixture is quite dry, add another couple of cups of water (you want it to be fairly loose and stew-like, so that the potatoes will be submerged and simmer; it will thicken as it cooks). Cook, uncovered, until potato is tender (about another 30 minutes, but you can simmer it longer - it only gets better). Add more water if at any point it is getting dry (and if you add too much water, simply simmer it down). Taste and add more salt at the end if needed. Stir in cilantro just before serving.