We grow globe eggplants in our garden every year. The skin on globe eggplants, because they're so small, is so thin and cooks really well when you bake it. If you're using small eggplants, you can leave the skin on eggplant parmesan. It also makes the meal a lot easier because you don't have to peel the eggplant. If you're using a large eggplant, though, the skin will be tough and chewy when you bake it. Eggplant skin is edible, but when it gets tough, it doesn't taste very good. So if you're using a large eggplant, you should peel it before making eggplant parmesan.