Dissolve cornflour in 1/2 cup water. Keep aside. Chop herb very fine, keep aside. Heat oil, add ginger, garlic, chillies, stirfry. Add chopped onions, celery, stir. Add remaining 1 cup water. Bring to a boil. Add sugar, salt, soya sauce, mint, herb, pepper. Add cornflour, stir and cook till sauce becomes transparent. Serve hot, with steamed rice, snacks, bhajias, and even soups.