This is great!! Balsamic vinegar and the pesto adds great flavor to the eggplant and mozzarella.
From EatingWell: July/August 2010
You can grill the eggplant rounds up to a day in advance, then assemble the eggplant, tomato and mozzarella “stacks” at the last minute. To make the eggplant and tomato stacks look symmetrical, use eggplant and tomatoes with approximately the same diameter.