If you like eggplant, then this dish is sure to please. It makes a great side dish or vegetarian main course. Although instructions are given here for baking the eggplant - a lower-calorie approach - you can also fry it in oil in a skillet on the stovetop, if you prefer. Either way, combined with a tasty marinara sauce and a combination of Italian cheeses, it's rich and satisfying. Try varying the recipe by adding a layer of cooked spinach or slices of thinly sliced prosciutto ham.
Position a rack in the middle of the oven and preheat oven to 375 degrees F. Place the slices of eggplant on a baking sheet (you may need 2). Brush each side with some of the oil and season lightly with salt and pepper. Bake until the eggplant is tender but not mushy, 10 to 20 minutes. Remove trays from the oven and let cool on a wire rack. Lower the oven temperature to 350 degrees.
Brush a 9x13-inch baking pan with pesto. Place half of the eggplant slices in the pan and top with half of the marinara sauce. Arrange all of the mozzarella on top of the marinara. Create a second layer with the remaining eggplant and marinara. Sprinkle the parmesan cheese on top of the gratin and place the pan in the oven. Bake until the gratin is hot and bubbling and the cheese has melted, about 30 minutes. Let rest 10 minutes before cutting; serve hot.