Chop the aubergine, courgettes and peppers into approximately 1cm chunks. Place the vegetables in a roasting tin in a single layer and drizzle over the olive oil. Season well with black pepper and roast for 25-30 minutes.
Meanwhile, weigh up 250g of ciabatta bread mix. Make up the ciabatta dough mix according to packet instructions, using only half the quantity of water and adding the chopped black olives when kneading. Set aside.
Remove the vegetables from oven and transfer into a round shallow ovenproof gratin dish or small non-stick roasting tin. Roll out the olive dough to approximately the same size and place on top of the vegetables. Press down well. Bake for 15-20 minutes. Remove from oven and allow to cool for a few minutes. Place a large serving plate on top of the gratin dish and carefully, tip out the vegetable crust. Give the bottom of the dish a few taps with a wooden spoon to make sure the veggies come away from the tin. Scatter the feta and basil over the vegetables and serve straight away.