Baked Ratatouille with Cheese Custard

In a 12-inch non-stick skillet heat 2 tablespoons oil over moderate heat until hot but not smoking and cook half of eggplant, stirring frequently, until golden brown and tender, about 6 minutes. Transfer cooked eggplant to a 2- to 2 1/2-quart gratin dish or other shallow baking dish. Cook remaining eggplant in 2 tablespoons oil in same manner and add to dish. In skillet cook onions, garlic, and red pepper flakes in remaining tablespoon oil over moderately low heat, stirring, until onions are softened. Add bell peppers and cook over moderate heat, stirring occasionally, until tender, about 8 minutes. Stir in remaining ratatouille ingredients and simmer, stirring occasionally, 5 minutes. Season mixture with salt and additional pepper and spoon evenly over eggplant. Preheat oven to 375 °F.