In a medium saucepan over low heat, combine the cornstarch, cold water, sugar, soy sauce, vinegar, sriracha, garlic, ginger and ground black pepper. Let simmer, stirring frequently, until sauce thickens and bubbles.
Place chicken pieces in a lightly greased 9x13 inch baking dish. Brush chicken with the sauce. Turn pieces over, and brush again.
Bake in the preheated oven for 20 minutes. Turn pieces over, and bake for another 15 minutes, until no longer pink and juices run clear.