Heat oil in a large cast-iron saucepan over medium-high heat. Pour in onions, raisins, garlic, nuts and red peppers. Cook, stirring occasionally until the onions are golden brown, about 5-7 minutes.
Add tomato paste, cocoa powder and 2 tbsp sugar. Cook for 2-3 minutes. Pour in eggplants, vinegar and water.
Cover and cook over medium heat, stirring occasionally, until the eggplant is soft and thick, about 7-10 minutes. Salt. Serve warm or chilled.