Prep the Eggplant: Cut the eggplants lengthwise into quarters, then slice them crosswise into 1½ inch pieces.
Fry the Eggplant: Pour 6 tablespoons (90 ml / 3 fl oz) of oil into a large nonstick wok or frying pan over medium-high heat.
Once hot, add the eggplant pieces and fry until lightly browned and about three-quarters cooked. Use a slotted spoon to transfer them to a bowl and set aside.
Mix the Sauce Base: In a separate bowl, whisk together the peanut butter and tahini. Slowly pour in 1 cup (240 ml) of boiling water, whisking continuously to form a smooth paste.
Stir in the tomato purée, brown sugar, and tamarind concentrate, followed by another 1 cup (240 ml) of boiling water.
Mix well and set aside.
Temper the Spices: Add the remaining 2 tablespoons (30 ml / 1 fl oz) of oil to the same pan over medium-high heat.
When the oil is hot, add the mustard seeds. As soon as they begin to pop (this takes only seconds), add the cumin seeds and sizzle for a few moments. Carefully add the crushed curry leaves—they will splutter—followed immediately by the chopped onion.
Sauté the Aromatics: Stir and fry the onion for about 3 minutes until it begins to brown.
Reduce the heat to medium-low and continue to cook for another 2-3 minutes.
Add the grated ginger and chopped garlic, and stir for 2 minutes until fragrant.
Build the Masala: Add the turmeric, ground coriander, ground cumin, and chili powder to the pan.
Stir for one minute, then pour in 1 cup (240 ml) of water.
Bring to a simmer and cook on low heat for 8–10 minutes to develop the flavors.
Combine and Simmer: Pour the prepared peanut sauce into the pan.
Cook gently for 5 minutes, stirring constantly.
Add the fried eggplant and salt.
Continue to cook on low heat for about 10 more minutes, stirring occasionally, until the eggplant is tender but still holds its shape. The sauce should be thick and luscious. If it becomes too thick at any point, stir in a splash of water.
Don't be afraid to taste and adjust the final dish. If it's too tangy, add a pinch more sugar. If it needs more brightness, a tiny squeeze of lime juice can lift all the flavors.
