Vegetarian Moussaka
This version uses eggplant only (no meat layer) and adds a layer of sliced mozzarella cheese.
Follow the meat moussaka recipe, but in place of the meat layer, spread the fried eggplant on the bottom of the pan with tomato sauce that has been spiced with a little cinnamon. Follow with a layer of sliced mozarella cheese and a final layer of eggplant. You will need more eggplant than the meat recipe calls for. A variation worth trying is to used breaded and fried eggplant (see the Eggplant Parmesan recipe); eggplant tends to soften quite a bit when it cooks and the breading will give it more structure.
Add a handful of Parmesan cheese to the custard sauce along with the eggs.