Heat 4 tablespoons (60 ml / 2 fl oz) of oil in a large, lidded frying pan or skillet over medium heat.
Once hot, add the sliced onions and fry for about 10 minutes, stirring occasionally, until soft and lightly browned.
Add the crushed garlic and grated ginger to the pan.
Sauté for another 2-3 minutes until fragrant and the raw smell has cooked off.
Add the eggplant batons along with 6 tablespoons (90 ml / 3 fl oz) of water.
Stir everything together, cover the pan with its lid, and cook for 15 minutes, or until the eggplant has softened and collapsed.
Stir once or twice to prevent sticking.
Remove the lid and add the tomato wedges, ground red chile, salt, turmeric, ground coriander, and ground cumin.
Continue to cook, uncovered, for 3-4 minutes, stirring until the tomatoes break down and become jammy.
Remove the pan from the heat.
Prepare for smoking.
Place a small, heatproof bowl (like a steel condiment cup) in the center of the curry, nestled into the eggplant.
Using tongs, hold the piece of charcoal over a gas flame or a lighter until its edges begin to glow red and turn white. This may take a minute or two.
Carefully place the hot charcoal into the small bowl inside the pan.
Put the lid on the pan and immediately carry it outdoors or to a well-ventilated area like a balcony.
Once outside, remove the lid, quickly pour the remaining 1 teaspoon (5 ml / 0.2 fl oz) of oil directly onto the hot charcoal—it will sizzle and smoke instantly. Immediately place the lid back on the pan to trap all the smoke.
Let the curry infuse for 1 minute for a subtle smokiness, or 2 minutes for a more intense flavor.
Carefully remove the lid, allowing the smoke to dissipate away from you. Use the tongs to remove the small bowl with the charcoal. Extinguish the charcoal by running it under cold water.
Taste the curry and adjust for salt or chile if needed.
Serve hot with fresh naan, roti, or basmati rice and a side of cooling yogurt.
