Sauté the onion and celery in a frying pan with a splash of olive oil until the onion colours a little and the celery retains a crunchy firmness.
Add the sugar and mix well to combine, deglaze with the vinegar and continue to cook until a little syrupy. Remove from the pan and set aside.
Add a good splash of extra virgin olive oil (evoo) to the pan, and fry off the eggplant (you may need to do this in batches if your pan isn’t big enough) adding a little more oil if needed and a little salt.
When the eggplant is almost cooked all the way through with a rich golden colour, add the diced tomatoes. Reduce the heat and continue to cook until the tomato has softened a little.
Add the onion and celery mixture along with all the liquid back into the pan with the eggplant. Mix well and then add the olives, capers, sea salt and freshly ground black pepper.
While the mixture is still warm, add the chocolate so that it melts and stir in gently. Then add the basil and adjust the seasoning if necessary.