1. Clean squid and cut each in 4 parts.
2. Blend together flour, cornstarch, baking powder and salt. Then beat egg and add, along with cold water and oil. Beat with an egg beater until batter is smooth. Dip squid in this batter to coat.
3. Meanwhile heat deep-frying oil. Add squid, a few pieces at a time, and deep-fry until golden. (Do not overcook.) Drain on paper toweling and serve.