1.Cut eggplants into thin slices, sprinkle with salt; stand in colander in sink 30 minutes. Rinse eggplant well under cold water; pat dry with absorbent paper.
2.Preheat oven to 180°C/160°C fan-forced.
3.Combine tomato, onion, celery, garlic, chopped oregano and parsley in medium bowl.
4.Using sharp knife, mandoline or V-slicer, slice potatoes into 2mm slices; pat dry with absorbent paper. Place half the potato in lightly oiled shallow 3-litre (12-cup) baking dish; top with half the eggplant, half the tomato mixture, then drizzle with half the oil. Repeat layering with potato, eggplant, tomato mixture and oil.
5.Cover dish with foil; bake in oven 1 hour. Remove foil; bake in oven about 30 minutes or until vegetables are tender. Sprinkle tiella with oregano leaves.