Heat 4 tablespoons of cooking oil in a pressure cooker on medium heat and add 1 teaspoon cumin seeds and ¼ teaspoon of hing powder (asafoetida). Fry for 10 seconds (for cumin seeds to slightly change color) and then add 1 cup chopped onion, 5 curry leaves, and 2 chopped green chilies.
Fry onion for 3 to 4 minutes or until it turns light pink and translucent. Then add 1 teaspoon ginger garlic paste (combined), ¼ teaspoon turmeric powder, and 1 teaspoon red chili powder. Fry on slow flame for 2 minutes and then add 1 chopped medium size tomato.
Keep stirring and frying on slow flame for 5 minutes.
Now add 2 cups chopped uncooked potatoes along with 1 cup of water, 1 teaspoon salt, and 1 tablespoon lemon juice. Stir well and place the lid. Cook for 20 to 25 minutes on medium flame.
Once the potato curry is cooked, mash the potatoes slightly to get a thick consistency, and then add chopped coriander leaves. Simmer the curry on low flame for 5 minutes.