Peel and dice the aubergines into 1 in (25 mm) cubes. To extract any bitter juices, place the cubes in a colander, sprinkle with 1 teaspoon of salt and allow to drain for 20 minutes. Slice the onion, pepper, celery and mushrooms and finely chop the garlic. Rinse the drained aubergines and pat dry.

Heat 4 tablespoons of oil in a casserole or frying pan. Saute the aubergines over medium heat. Stir constantly until softened and slightly coloured. Remove the aubergines and put to one side, then add the onions, garlic, pepper and celery. Cook for 6-8 minutes, stirring occasionally, until quite soft.

Chop and peel the tomatoes and add to the pan along with the mushrooms and capers. Turn down the heat and simmer for 5 minutes, until the tomato sauce has reduced and thickened. Stir in all the aubergines, oregano, olives, vinegar and sugar.

Simmer for another 15 minutes, adding a little water if it is too thick. Season with salt and black pepper, sprinkle with pine nuts and serve.