Make the Yogurt-Coconut Sauce: In a blender, combine the yogurt, ginger, green chilies, and coconut.
Blend until completely smooth. Pulse in the garam masala, then set the sauce aside.
Temper the Spices: Heat the ghee in a large, heavy-bottomed pan or saucepan over medium-high heat.
Add the mustard seeds and cumin seeds.
Once the mustard seeds begin to pop, stir in the curry leaves and asafetida.
Fry the Potatoes: Immediately add the steamed potato cubes to the pan.
Stir-fry for 3 to 4 minutes, allowing them to get slightly golden and coated in the spices.
Combine and Simmer: Pour in the yogurt-coconut sauce.
Add the turmeric, ground coriander, steamed eggplant, salt, and half of the fresh coriander. Gently toss to coat everything evenly.
Finish and Serve: Reduce the heat and cook, stirring gently, until the sauce thickens and clings to the vegetables. Just before serving, stir in the fresh lemon juice and garnish with the remaining fresh coriander.