Thinly slice the eggplants and sprinkle with salt. Place in a colander in the sink or suspended over a large bowl. Leave for 30 minutes while they lose their bitter liquid.
Preheat oven to 180 degrees C. Lightly grease a 23x33cm baking dish with olive oil.
Meanwhile, sauté the onions, garlic, and olive oil in a large frying pan over low heat, covering the pan with a lid to keep them moist. Sauté the onions until they are soft and translucent.
Add the basil, oregano, passata, water, salt and pepper to the onions. Simmer 10 minutes.
Rinse off the eggplant slices and place them on a baking tray lightly greased with olive oil to prevent sticking. Bake for 5 to 10 minutes while tomato mixture is simmering.
In the prepared baking dish, spread 2 to 3 tablespoons of the tomato mixture over the bottom.
Remove eggplants from the oven and arrange one layer of eggplant on the bottom of the dish. Pour one third of the tomato mixture over the eggplant. Pour half of the yoghurt over the tomato mixture. Repeat the layers and top with the remaining tomato mixture.
Cover dish with foil and bake for 30 minutes. Uncover and sprinkle the wheatgerm or breadcrumbs over the top, followed by the parmesan cheese. Bake for another 20 to 30 minutes or until topping is golden brown and eggplants are soft.