Stir the water, cornstarch, soy sauce, gochugaru, and sugar in a bowl and set aside.
In a saucepan over medium heat, add 1 tablespoon of olive oil. Add the minced garlic and cook for 30 seconds to a minute, stirring frequently.
Give the soy sauce mixture a quick stir again, in case any cornstarch settles to the bottom. Carefully pour the liquid into the saucepan.
Once the liquid reaches a boil, reduce the heat to medium-low and let it simmer for another 2 minutes to thicken slightly.
Turn off the heat and add the miso to the saucepan and whisk to incorporate. Set the sauce aside.
Rinse the eggplant and pat dry. Peel off the petals from the top of the eggplant and slice off the remainder of the stem.
Slice the eggplant lengthwise into ¼ to ½-inch thick planks. Make several diagonal cuts to pierce the skin.
Brush both sides of each slice of eggplant with olive oil and sprinkle with salt.
Preheat the air fryer to 400ºF (205ºC). Add the eggplant slices to the basket in a single layer. Cook for 4 minutes, flip, and cook for another 3 to 4 minutes.
Transfer the cooked eggplant to a serving plate and continue air frying the remaining eggplant.
Spread miso sauce over all the eggplant slices. Garnish with sesame seeds and scallions.
For eggplant chunks, slice diagonally and toss with olive oil and salt. Cook in the air fryer for 6 to 7 minutes.
Toss the cooked eggplant with about ¾ of the miso sauce. Garnish with sesame seeds and scallions.
Serve with jasmine rice or egg fried rice.
No air fryer? You can bake the eggplant on lined baking sheets at 400ºF (205ºC). The eggplant will take twice as long to cook.
