1 cup ice water
1 egg
1/4 teaspoon baking soda
1/4 teaspoon salt
2 cups all-purpose flour, divided
4 skinless, boneless chicken breasts, cut into cubes
vegetable oil for frying
Sauce:
2 tablespoons cornstarch
2 tablespoons water
1 cup white sugar
1/2 cup ketchup
1/2 cup white vinegar
1/2 cup water
1/2 cup orange marmalade
1/2 cup chopped fresh pineapple (optional)
2 tablespoons pineapple juice
2 teaspoons soy sauce
1 teaspoon minced fresh ginger root
1 teaspoon minced garlic
1/4 teaspoon cayene pepper

Beat ice water and egg together in a bowl using a whisk or a fork.
Add baking soda and salt and mix to combine.
Add 1 cup flour to water mixture; mix until blended but lumpy.
Place remaining 1 cup flour in a separate bowl.
Cover each piece of chicken in flour, then move to egg mixture and cover, letting excess batter drip off.
Heat vegetable oil in a wok or large, deep frying pan over medium heat until a drop of water crackles when placed into oil.
Place chicken into the hot oil and fry, flipping if needed, until no longer pink in the center and golden brown. Set aside and keep warm.
Combine cornstarch and 3 tablespoons water in a small bowl.
Combine sugar, ketchup, vinegar, 1/2 cup water, orange marmalade, pineapple, pineapple juice, soy sauce, ginger, garlic, and cayene in a medium saucepan. Bring to a boil; add cornstarch mixture. Reduce heat and let simmer, stirring frequently, until desired thickness is reached.
Pour sauce over chicken and serve.

Notes
Make sure to bring the orange mixture to a boil, otherwise it will be starchy.