Preheat the oven to 180 degrees
Cut the aubergine into large chunks or thick (2 inch) discs and the courgettes into thick strips (if using); brush a baking tray with a little olive oil and lay out each vegetable on a (separate) baking tray taking care not to overlap. Lightly drizzle the top with a little more olive oil, season with salt and pepper and roast in the oven; the aubergines will need 35-40 mins until soft and golden and the courgettes will need 20-25 mins until soft. Set aside.
Meanwhile, in a saucepan, gently sauté the onions and garlic in olive oil until they are soft for around 8-10 mins. Season with salt and pepper and add the tin tomatoes and purée. Check seasoning. Bring to the boil and simmer over a low heat until the sauce has reduced and thickened - around 10 mins.
Now begin arranging...in a deep dish, begin with a layer of tomato sauce and arrange a layer of the roasted aubergine, followed by a thin layer of chickpeas and a sprinkle of mixed spice. Drizzle with olive oil and repeat with the courgettes. Continue and finish off with a layer of tomato sauce over the top. If necessary, double up on the vegetables on one layer.
Bake in a moderate oven (180) for 1 hour. Cover and allow to settle for 15-20mins if possible before serving. Serve with a rocket/watercress with feta salad on the side.