Cut the eggplants diagonally into 1 cm thick slices. Cut the leek into 1-2 cm wide diagonal slices.
Heat some sesame oil in a frying pan, add the vegetables from step 1 and stir fry. If you want to use very little oil put a lid on and steam-cook the eggplant.
Add the ponzu and sugar (it's best if you mix them together beforehand) to flavor the eggplant. Transfer to serving plates and sprinkle with bonito flakes.
Story Behind this Recipe
I had just a little ponzu sauce left.
If you use the eggplant as soon as you cut it, you don't need to do anything to remove any bitterness. If you do do so, by soaking it in water, be sure to drain it very well. In step 2, you are pan-drying rather than stir-frying. Be careful not to let the eggplants burn. If you want to reduce the amount of oil used, steam-frying should work.