Place a wok on the gas stove and heat it. Once the wok is hot, add 3 tbsp of mustard oil and allow it to heat up.
When the oil is hot, add cumin seeds. Sauté them until they emit a fragrant aroma, then add the chopped onions. Sauté the onions for 3 minutes.
Once the onions are sautéed, add the chopped tomatoes and sauté for an additional 2 minutes.
When the tomatoes have cooked down and lost their moisture, introduce the ginger-garlic paste. Stir until the raw smell evaporates.
Once the raw smell of the ginger-garlic paste is gone, incorporate turmeric powder, cumin powder, Kashmiri red chili powder, and regular red chili powder. Stir and thoroughly mix the spices.
To prevent the spices from burning, add a small amount of water. Stir continuously for 5 minutes, and then add just under 1 tbsp of salt. Mix well.
Add the boiled potatoes and stir them into the mixture. Afterward, pour in 1 cup of water and add the green chilis. Cover and let it simmer for 5 minutes.
Uncover the wok; the curry should be nearly done. Add the roasted spice powder and mix it in. Cover it once more.
Uncover the wok; the curry should be ready at this point. Add the chopped coriander leaves and turn off the gas. Allow the curry to rest for a few minutes.
Transfer Potato Curry into a bowl. Serve it with steamed white or brown rice, paratha, roti or chapati.