Put the garlic cloves on a sheet of foil and place on the upper rack of the halogen oven. Set the temperature to 250°C (482°F) and cook for 5–10 minutes until the garlic is soft. Be careful not to let it burn.
Cut the aubergine into 12 slices each about 1 cm (½ inch) thick. Layer the slices in a colander, sprinkling each layer with salt. Leave to stand for 30 minutes. Rinse thoroughly to remove all the salt and pat dry on kitchen paper. Brush the slices with the oil. Fry in a large frying pan on the hob, turning the slices once, for about 5 minutes until golden on both sides. Leave to cool.
Meanwhile, mash the softened garlic against the sides of a bowl. Stir in the diced tomatoes, sun-dried tomatoes, tomato paste and basil. Season to taste.
Make the stacks. Arrange 4 aubergine slices side-by-side in a shallow roasting tin and spread each one with a little pesto. Spoon a little of the tomato mixture on top, then place another aubergine slice on top of that. Spoon over a little more tomato mixture, then add another slice of aubergine. Spread with the remaining pesto. Place a piece of mozzarella on top of each stack, securing in place by pushing a skewer down through the centre of the stack. Place the tin on the lower rack of the halogen oven.
Set the temperature to 225°C (437°F) and cook for about 10 minutes until the stacks are heated through and the mozzarella is soft. Transfer to serving plates, drizzle with balsamic vinegar and garnish with rocket or basil leaves. Serve as a starter or to accompany lamb dishes.