Cut the eggplants in half lengthwise, then cut crosswise into 1cm thick slices. Soak in water for 10 minutes, then drain well.While the eggplant is soaking, cut the piman in half, remove the stem and seeds, and cut into rough bite-sized pieces.Mix the sweet miso sauce ingredients together, adding a few drops of soy sauce if it tastes too sweet, or of water if it’s too salty.
Heat a frying pan to medium-high, add the vegetable oil and stir fry the eggplant for a couple of minutes. Cover with a lid and lower to medium, allowing the eggplant to steam for 3 minutes.
Add the piman and stir fry for a few minutes, making sure not to overcook – it should provide a contrast in texture with the soft eggplant.
Add the sweet miso sauce mixture to the pan and continue stir frying until the liquid has almost evaporated.