In a large frying pan (for which you have a lid), add the oil and warm-up; once warm add the eggplant, onion, and garlic and cook on medium heat until the eggplant cubes are nearly cooked. The time required will mainly depend on the size of the cubes and of the pan; I normally chop the eggplant into half inch (1-1.5cm) cubes and use a pan big enough that it only fills up about 3-4 cm and it takes me 10 minutes approximately on a low/medium flame.
While the eggplant cubes are cooking, roughly chop the green olives and wash the basil leaves, and set aside.
Once the eggplant pieces are nearly cooked, add the salt, pepper, capers, and green olives, mix well and then add the passata and one cup of water (I usually put the water in the passata box to ‘clean the tomato out’).
Bring to the boil, put the lid on, and leave to simmer on low heat for about 25 minutes or until the passata is cooked and you reach the consistency you like.
Once ready, sprinkle the basil leaves on top, adjust the seasoning, mix and serve.