Peel the potatoes and cut into bite-size pieces. Rinse the eggplant, halve, quarter and cut into bite-size pieces. Rinse the chile peppers, halve, remove the seeds and cut into strips. Peel the onions and cut into thin columns. Peel and finely chop the garlic. Place the eggplant pieces in plenty of salt water for about 15 minutes. Squeeze out the eggplant and pat dry.
Heat the ghee in a large pan. Saute the eggplant pieces until completely golden. Add the cumin and coriander. Saute briefly. Reduce the heat and stir in the onions and garlic. Saute for about 2 minutes. Add the chile peppers, potatoes and mustard seeds. Pour in the coconut milk, season with salt and reduce the heat. Cover and simmer for about 10-15 minutes. Add the curry. Serve hot.