Combine chicken pieces with water baking soda and salt in a large bowl and stir vigorously until the water is mostly absorbed by the chicken.
Add eggs to the chicken mixture and stir until fully blended, then incorporate cornstarch until no dry bits remain; finish mixing in the oil until evenly coated.
Pour 2 to 3 inches of oil into a wok or deep pan and heat it to 375°F.
While the oil heats, whisk together orange juice orange zest ketchup sugar vinegar and cornstarch in a bowl then set aside.
Carefully drop the chicken pieces one by one into the hot oil in a single layer without overcrowding and cook for 4 to 5 minutes.
Remove chicken from oil and drain for 2 to 3 minutes, stirring occasionally during frying to separate any sticking pieces.
Return the oil temperature to 375°F and fry the chicken a second time for 5 to 6 minutes until they turn golden brown and crispy.
Drain the fried chicken on paper towels or a wire rack.
In a wok or large skillet over medium heat add a bit of oil and once hot toss in the white parts of the green onion along with minced garlic and chili flakes or whole chili pepper; stir for about 10 to 15 seconds until fragrant.
Give the orange sauce a quick stir and pour it into the wok, then increase the heat to medium-high and cook the sauce until it bubbles thickens and becomes glossy, stirring often to avoid lumps.
Add the double-fried chicken into the sauce and toss well to coat every piece evenly.
Serve the orange chicken immediately garnished with the green parts of the green onion alongside steamed white or fried rice. Enjoy!