Heat oil in a pressure pan and add the mustard and the cumin seeds.
When the seeds splutter, add curry leaves, garlic paste, and finely chopped onions. Add salt to let the onions colour evenly. When they turn brown, add dhania powder, turmeric powder and asafoetida, and fry for a minute.
Then add the brinjal and fry for a few more minutes.
Add tamarind paste with just enough water to submerge the brinjal. Let the mixture pressure cook.
After two whistles, switch off the heat and wait until the steam is gone. Mash the mixture well.