Wash the potatoes clean thoroughly. Prick holes all over the potatoes using a fork. Place them in salted water for 2-3 hours. This allows the salted water to reach the inside of the potatoes and impart flavor.
In a wok, bring the oil to heat, add the asafetida.
As it sizzles, add the tomatoes, the ginger and all spices except garam masala. Stir for five minutes until the tomatoes break down and the spices give out a subtle aroma.
Add the curd and stir vigorously for another five minutes so it is well incorporated with the spices. It usually avoids the gravy from curdling too. I usually use a whisk here as it makes vigorous mixing easier.
Stir in the potatoes, coating the gravy well into them. Add salt.
Next, add a cup of hot water, cover the wok and leave the potatoes to cook and the curry to dry up. You need to lift the lid every couple of minutes and give the potatoes a good stir.
When the curry is completely dry and a fork can be inserted through the potatoes easily, the dish is ready. Mix in the garam masala and take the wok off the flame.
This dish is spicy and infinitely more delicious when served the next day.