Heat a kadhai with mustard oil.
Splutter mustard seeds.
Add curry leaves.
Then add onion paste. Saute for some time. Then add ginger garlic paste.
Saute all together till the rawness is gone.
Next, add tomato puree. Add salt, turmeric powder, and Kashmiri lal mirch
Mix and cook all together.

Meanwhile, prepare posto paste.
In the grinder jar having posto and water, add soaked cashewnuts and green chilies. Make a smooth paste.

Now check the masala.
If you get a nice aroma and masala is leaving oil, then add in the boiled potatoes.
Add little water and give a nice gentle mix, so that potatoes are nicely coated with the masala.

Continue cooking in slow to medium heat for some time.
Next, add the prepared posto paste to the potatoes. Reduce heat.
Add little water and give a nice mix.
Now cover and cook till the rawness of posto is lost.

Next, add water to make it curry consistency. Continue cooking at medium heat.
When all the flavours combine well, finish off by adding garam masala.
Cook on medium heat for some more time.
By now you will be getting a nice... aroma.