Wash the long brinjals under running water, cut and discard the stalk. Chop them lenghtwise in to 1 inch pieces. Keep them immersed in water to avoid discoloration.
Soak tamarind in 1/4 cup of water for about 10 minutes.
Method
In a pressure cooker add oil, mustard seeds and lentils. Saute in medium flame till the mustard seeds start spluttering. Then add chopped green brinjals and turmeric powder. Saute for a while.
Extract tamarind juice and discard the residue. Include this tamarind juice in the seasoning, then add jaggery and vangi bath powder. Combine everything well. Now add washed rice.
Finally add 2 cups of water and salt. Close the lid and pressure cook for 3 whistles in medium flame. Switch off once done.
As the pressure subcides fluff the vangi bath and serve with cucumber raita.
Notes
I have used regular sona massori variety rice, you can use basmati rice too .Rice to water ratio remains 1:2.
Cucumber raita goes very well with vangi bath, I recommend it.
Alternatively you can cook rice first and then mix with seasoning as in step2.