Rub the oil over the aubergines and season well. Place them under a hot grill and cook for 5–7 minutes on each side or until soft and golden brown.
Mix together the passata, tomatoes, chilli and oregano and season well. Arrange the aubergines, cut side up, in the grill pan, spoon a little of the passata mixture on top of each aubergine and place some mozzarella slices on top. Return to the grill and cook for 2–3 minutes until the mozzarella has just melted.