Slice the eggplant, sprinkle with salt and let it sit for an hour. Use paper towel to soak up any excess water. Toss the eggplant pieces in cornstarch. In a wok at medium heat, add oil, and then add the eggplant once the wok is hot. Cook until eggplant is tender, stirring frequently. Meanwhile, stir together soy sauce, sugar, ginger, and garlic in a bowl. Add the sauce to the wok, coating the eggplant. Sprinkle with desired amount of red pepper flakes and sesame seeds.