Cut the eggplant into thin 1-1/2-inch by 3-inch slices. Do not peel them. For the batter mix the flour, water, and salt together in a small bowl, then strain through a fine sieve. Let rest for about 20 minutes. For the sauce, heat a wok or large frying-pan until hot and add the 1 tablespoon of oil. Put in the scallions, ginger, and chili bean sauce and stir-fry for 30 seconds. Then add the stock, rice wine, vinegar, tomato paste, sugar, and soy sauce and continue to cook for 1 minute. Thicken the sauce with the blended cornstarch and cook another minute. Set aside. Heat the oil in a deep-fat fryer or large wok until quite hot. Dip the slices of eggplant into the batter, let the excess batter drip off, then deep-fry. You may have to do this in several batches. Remove from the oil with a slotted spoon and drain well on paper towel. Arrange the eggplant slices on a serving platter, pour the sauce over and serve.