Add roughly chopped tomatoes and sliced ginger to a blender and make a fine puree.
Mash half the boiled potatoes and dice the remaining half into roughly 2cm sized cubes.
In a large pan, heat the oil. Fry asafoetida, cumin seeds and chillies.
Add the coriander powder, turmeric, chilli powder and salt. Fry well. Add splash of water and mix well to prevent the spices from burning.
Add the mashed potatoes and toss well in this spice mix.
Add tomato-ginger puree and bring to a boil. Reduce flame, add the diced potatoes and simmer for 5-7 mins.
Garnish with coriander and ginger.
Serve with rice, rotis or puris.
Add 1 teaspoon sugar to the curry while it is simmering, if tomatoes are very sour.
For added flavour, add 1/4 tsp of fenugreek seeds to the oil along with cumin seeds or 1/2 tsp of fenugreek powder along with the spice powders into the oil.
I would not recommend using store-bought tomato puree (tetrapaks) for this recipe as the flavour of fresh tomatoes is very important in this curry. The tetrapak tomato puree brands do have a sharply tart taste with the unmistakable smell of preservatives used. However, if you do get canned tomatoes, blend that up and use it by all means.
One of following ingredients can be added to the curry along with the potatoes and it will go very well – frozen peas / small cubes of paneer / finely chopped methi (saute and then add) / small chunks of cooked soya nuggets /a small portion of cooked chickpeas or black-eyed peas.