Soak tamarind in rice washed water and take tamarind juice. (rice washed water will be white color as it will have washed starch from rice)
In a pressure cooker heat oil. Add fenugreek seeds, mustard seeds. Once the mustard seeds stop splattering. Add green chili, shallot (sambar onion) and sauté until the onion turns translucent (golden brown).
Now add tomato, chili powder and sauté until they become mushy.
Now add brinjal (egg plant) , potato, salt and sauté until they are coated well.
Now add tamarind juice and pressure cook for 1 whistle. Once the pressure is gone. Re cook it until the mandi becomes thick and oil start to seperates.
This goes well with lemon rice, tamarind rice. It well suite for travelling