Air-fry the eggplant and potatoes: Place the eggplant slices in the air fryer basket and air-fry at 375 degrees for 10 minutes, tossing the basket halfway through to ensure everything cooks evenly. Repeat with the potato slices. You can coat the veggies with a bit of oil if you want before you air-fry but it is not necessary. Alternatively, if you don't have an air-fryer, fry the vegetables in a couple of tablespoons of oil until they are semi-tender. You can also toss the vegetables with a bit of oil, arrange them on a baking sheet in a single layer, and broil them on high for 5-10 minutes.
Blend the masala ingredients: Place the masala ingredients--onions, tomatoes, ginger garlic paste and peanuts--in a blender and blend into a smooth puree. Set aside.
In a wok or saucepan heat the oil. Add cumin seeds and, when they sputter, add the blended masala paste. Be sure to keep the heat low when you do this as the masala will sputter and bubble.
Add remaining spices: These are garam masala, turmeric, cayenne or paprika, ground coriander and ground cumin. Add ½ teaspoon of salt. Mix.
Cover the wok and cook for 10 minutes over medium heat or a medium flame until the masala is darker and glossy. Stir a few times in between so the masala doesn't stick. A good indicator of whether a masala paste has cooked is to check for droplets of oil separating and floating on top. Because we use very little oil in this recipe you likely won't see droplets on top but a glossier look and a darkening of the tomato paste is a good indicator that the masala is ready.
Add the eggplant and potato slices to the wok. Mix them in and add ½ to 1 cup of water at this point to create a sauce. Cover again and let the veggies cook until they are tender. Check for seasoning and add more salt if needed.
Garnish with cilantro or mint and serve hot.