Heat oven to 200C/fan 180C/gas 6. Brush the slices of aubergine with the olive oil and place on a baking
tray with the whole red peppers. Bake for 15-20 mins until the aubergine slices are golden brown and tender and the peppers are charred and blistered. Place the peppers in a plastic bag, seal and leave aside to cool.
When the peppers are cool, cut in half and remove the blackened skin and seeds. Cut into thick strips. Halve the tomatoes, remove any seeds and juice, then pat dry on kitchen paper. Thinly slice.
Roll out half the pastry on a lightly floured surface, then use to line a 20cm pie plate. Arrange half the aubergine slices in the pastry case and top with half the peppers. Season between each layer. Arrange half the mozzarella cheese on top, then cover with half the tomato slices.
Sprinkle over half the black olives, oregano and basil. Repeat these layers, using the remaining ingredients.
Brush the pastry border with water. Roll out remaining pastry and use to cover the pie, trimming the edges and pinching together to seal. Brush with the milk, place on a baking sheet and bake for 25 mins until crisp and golden.