CUT EGGPLANT into 1/2-by-2-inch strips. If using Italian eggplants, peel skin. In a colander, toss eggplant with salt; drain for 30 minutes. Squeeze gently to remove excess water. Pat dry with paper towels. In a small bowl, mix soy sauce, sugar and chicken stock. Preheat wok until hot over high heat. Add 3 tablespoons of the oil, tilt wok to coat sides. When hot, add 1 layer of eggplant, stir-fry until seared and tender (about 3 minutes). Remove to colander. Drain over a bowl to catch juices. Cook remaining eggplant in same manner adding more oil if needed. Reheat wok over medium-high heat. Add remaining 1 tablespoon of the oil, ginger, garlic and chile; cook gently but do not brown. Add water chestnuts and half of the green onions; stir-fry together for 5 seconds. Increase to high heat, add reserved soy sauce mixture and eggplant juices; bring to a boil. Return cooked eggplant; toss quickly over high heat until most of the sauce is reduced and absorbed into eggplant (about 1-to-2 minutes). Fold in vinegar and sesame oil. Remove to serving dish. Top with remaining green onions and sesame seeds. Serve hot or cold.