Boil potatoes in a pot of water. Let cool, peel, and cut into approximate equal size 1 inch pieces.
Heat 1 tablespoon oil in a pan on medium heat. Add cut potatoes and mix well. Let cook about 4 minutes or until you get a bit of browning. Remove potatoes and place on the side.
In same pan, add remaining 2 tablespoons of oil and heat at medium heat. Add kalonji, cumin seeds, mustard seeds, and a pinch of asafoetida. Let the seeds splutter.
Add garlic ginger paste. Sauté for a minute until fragrant. Add onions and let cook 2 minutes.
Add green chilies and mix. Follow that with kashmiri chili powder, turmeric powder.
Add the peeled and cubed potatoes, salt, and achari spice mix. Mix well to coat them with the spices.
Add water, mix, and cover pot. Let cook five minutes ,allowing the flavors to meld and the spices to infuse into the potatoes. .Stir occasionally to prevent sticking.
Once the potatoes are cooked through and tender (check with a fork or a knife), turn off gas and finish the dish with chopped cilantro leaves.
Serve the Achari Aloo hot as a side dish with roti, naan, or rice.