Prepare the Spice Slurry: In a small bowl, combine chickpea flour, half of the turmeric powder, salt, and red chili powder. Gradually add water, mixing until a smooth, thick slurry forms. Set aside.

Cook the Potatoes: Bring a large pot of water to a boil, add the diced potatoes, and parboil for about 5-7 minutes, or until they’re just starting to soften. Drain and set aside.

Sauté the Spices: Heat vegetable oil in a large skillet over medium heat. Add mustard seeds and wait until they start to pop, then add cumin seeds (or cumin powder) and the remaining turmeric powder. Sauté briefly until the spices are fragrant.

Combine and Cook: Add the parboiled potatoes to the skillet, stirring to coat them with the spiced oil mixture. Pour the chickpea flour slurry over the potatoes, mixing well until each potato piece is evenly coated.

Finish Cooking: Continue to cook over medium heat, stirring occasionally, until the potatoes are golden brown and crispy on the edges. This should take about 10-12 minutes.

Serve: Transfer the Bombay potatoes to a serving dish. Garnish with fresh cilantro if desired and serve hot as a side or snack.