Fry the onions and garlic till the onions are really soft – that’s the bottom layer of your thing.
To prepare eggplant: put round slices of well-oiled eggplant on trays and bake for about 25 minutes, after having oiled them on both sides. You might also want to salt them beforehand and place heavy stuff on them to get the juices out.
Slice up tomatoes and eggplants into discs, place a layer of eggplants alternated with tomatoes, then a layer of feta/mint/olives crumbled randomly in between each layer of tomato and eggplant. Repeat until your tomato and eggplant is finished.
The top layer is a mixture of breadcrumbs and olive oil with optional pine nuts. Parmesan is probably also a rather tasty addition.
Once constructed the whole thing should bake for about 60–70 minutes at about 180°C.