Bombay potatoes are a staple Indian dish of tender potatoes tossed in spices and served with fresh cilantro. Serve this recipe as an appetizer or flavor-packed side dish.
If the baby potatoes are more than 2 inches across, cut them in half. Transfer the potatoes to a medium pot. Add 1 teaspoon salt and 1/2 teaspoon turmeric. Pour enough water to cover the potatoes by about 1 inch, cover with a lid, and bring to a boil over medium-high heat. Once boiling, remove the lid and reduce the heat as needed to maintain a boil. Cook the potatoes until a knife is easily able to pierce the potatoes but they are not completely soft, 10 to 15 minutes. Reserve 1/2 cup of the cooking liquid, then drain the potatoes.
In a large skillet over medium-high heat (cast-iron or nonstick work well here), add the oil. Once hot, add the drained parboiled potatoes. Pan-fry the potatoes, stirring often, until golden brown, 2 to 4 minutes. Transfer the potatoes to a plate, leaving as much oil as you can in the pan.
In the same skillet over medium-low heat, add the cumin and mustard seeds and let them start to sizzle—you will hear a crackling sound. Add the onion, serrano pepper, ginger, and garlic. Stir well and let cook for 1 minute. Add the remaining 1 teaspoon salt (or to taste), 1/2 teaspoon turmeric, garam masala, cumin, Kashmiri chili powder, and coriander, and stir to combine. Add the tomato paste, stir well, and add the 1/2 cup of reserved cooking liquid. Increase the heat to medium and let the mixture simmer so a little of the liquid evaporates and the spices and tomato paste are fully incorporated, 1 to 2 minutes.
Stir the potatoes into the masala mixture. Sauté until the potatoes are tender and the masala has thickened and coated the potatoes, 3 to 4 minutes. Remove from the heat and stir in the lime juice, taste, and adjust the seasoning as needed. Garnish with fresh cilantro and serve with yogurt and roti, if desired. Transfer the leftovers to an airtight container and store in the fridge for up to 4 days. Reheat in the microwave as needed before serving.