How to Make It
Preheat oven to 450°F.
Trim stems from eggplants. If using medium eggplant, cut in half lengthwise. Cut small eggplants or medium eggplant halves into 7 slices each, cutting to, but not through, stem end. (Eggplant should be able to be fanned out without falling apart.)
Rub a 13- x 9-inch gratin dish with crushed garlic clove. Drizzle 1 tablespoon olive oil in bottom of dish, and rub to coat evenly. Place 2 cups onion slices, thyme, marjoram, coriander, and one-third sliced garlic in an even layer in prepared dish. Arrange eggplants on top, and sprinkle with 3/4 teaspoon salt. Place 1 tomato slice between each eggplant “fan blade.” Sprinkle with pepper and remaining 3/4 teaspoon salt. Top with remaining sliced garlic, remaining 2 cups onion slices, mushrooms, olives, and bay leaves. Drizzle with remaining 1/3 cup olive oil.
Cover dish tightly with aluminum foil. Bake in preheated oven 15 minutes. Reduce oven temperature to 375°F (do not remove dish), and cook until eggplant is almost tender, about 1 hour and 10 minutes. Remove and discard foil, and bake until juices are slightly reduced and eggplant is very tender, about 20 minutes. Garnish with torn basil.
Baked gratin also holds well covered and refrigerated overnight. Serve warm or at room temperature.