In a medium bowl mix together all of the sauce ingredients and set aside.
In a large bowl add flour, cornstarch, baking powder and salt. Add water slowly until a semi-thick batter has formed.
Heat oil in a deep-fryer to 375 degrees Dip each chicken piece in the batter and place into the deep-fryer. Deep-fry the coated chicken pieces in batches until golden and crispy and fully cooked (the internal temperature has reached 165 degrees F.). Drain on a plate lined with paper towels.
Add the sauce to a saucepan and summer until thick and glossy.
Mix the fried chicken pieces with the sauce and toss well.