Combine ginger, green chilies & coconut in blender with 1/3 cup of water till smooth. Add garam masala & pulse for a few seconds. Set aside.
Heat ghee. Whe hot, add mustard & cumin seeds & fry for a few seconds. Stir in the asafetida & almost immediately put in the potatoes. Stir fry for 5 minutes Then pour in the mixture from the blender. Add the turmeric, coriander, eggplant, salt & half the fresh coriander. Mix very gently so as not to break the vegetables.
Reduce heat & fry very gently until the liquid has evaporated. Mix in lemon juice & remaining coriander greens & serve.
Yamuna Devi, "The Art of Indian Vegetarian Cooking"