Preheat oven to 425F.
Coat eggplant in ½ of the olive oil and some salt and roast in hot oven until browned.
Remove from oven and allow to cool.
When the eggplant is cool enough to handle, chop into small pieces.
Heat remaining olive oil in saute pan.
Cook onion and celery on medium-low heat for 15 minutes, or until the onions are soft.
Add the fresh garlic and minced black garlic and cook for an additional 2 minutes.
Add the red bell pepper and green bell pepper and diced tomatoes and cook for an additional 10 minutes.
Add the roasted eggplant you cooked earlier, in addition to the black olives, sherry vinegar, and sugar.
Cook mixture for an additional 5 minutes.
Taste and adjust acidity and sweetness.
Season with salt and freshly-ground black pepper.
Allow to cool and serve at room temperature, on top of warm crostini.