Heat 5 tablespoon of sesame oil in a pan. When oil is hot enough , add mustard seeds , curry leaves and broken red chillies.
Add chana dal , urad dal and cashews and saute till it turns golden brown.
Now add sliced onions and fry well till onion turns translucent.
Add thinly sliced capsicum of 1 ½ " inch and fry well.
Add chopped tomatoes and potatoes .Mix well and saute for a minute.
Add ½ teaspoon of turmeric powder , 1 teaspoon of salt and continue to cook till potatoes and tomatoes are well cooked.
Add 3 tablespoon of Vangi bath masala powder and mix well . Now add in ½ cup of tamarind juice extracted from ½ tablespoon of tamarind pulp and mix well.
Add ½ teaspoon of jaggery powder , 1 teaspoon of salt and mix well.
Keep the flame on low , mix well everything and cook till oil releases from the edges.
Mix well everything. Turn off the flame and set aside till use.
Once cool , you can even store it in a clean dry glass jar upto 1 week in refrigerator.