First, take 4 potatoes and put with water in the cooker, the Water level should be the same as the level of potato in the cooker. Pour tamarind into water 10 minutes, to create a tamarind pulp.
After that put tamarind into a mixer jar with little water.
Grind the tamarind into the mixer and prepare pulp.
Peel off the potato, mash them with hand only.
Chop both green chilly and red chilly into pieces.
Put kadai or fry pan on the gas on the high flame.
Add 2 tsp desi ghee in the kadai.
Check if the desi ghee is hot then add chopped chilly and cumin seed in the desi ghee.
Once cumin seed starts crackling and green chilly become a little fade in green color.
After that add mashed potato into kadai.
Fry potato with a spatula.
Fry potato for one minute, after that, add 4 tbsp tamarind pulp, if you don't want more sourness then reduce the quantity of tamarind.
Mix tamarind with a spatula.
After 30 seconds, add 400 grams of water.
Add fasting salt / senda salt to the curry. Let cook the curry on medium flame.
Meanwhile, similarly, chop the green coriander.
After that add the water in the curry if needed, In this curry, water should be more than the potato or content.
At the same time sprinkle chopped green coriander.
Check if salt is proper, make it balance.
To make gravy little thick mash some potato in the curry.
Let cook curry for 15 minutes on the low medium flame.
It will add flavor to the curry.
Once the curry is properly flavored.
Transfer in the bowl and while serving sprinkle chopped green coriander.