In a large pan, heat oil on medium heat for 2 minutes.
Add in the mustard seeds and let them splutter.
Add in the curry leaves and hing and give it a mix
Add in the coriander seeds, cumin powder, ginger, garlic and chili and cook for 2 minutes
Add in the potatoes and turmeric and mix well to coat. Cook for 2-3 minutes
Add in the eggplants, tomato and salt and mix well to coat with all the spices.
Cover and cook on low heat for 15-20 minutes stirring occasionally. I like my eggplants well cooked so i cook the dish for a few minutes longer. My mom likes hers just about done and not very mashed, so she cooks on low heat and doesnt stir it much.
Serve hot garnished with freshly chopped cilantro leaves, with Rotis or Naan and a side dish of Daal(lentil curry)