In a medium bowl, mix together the baking powder, salt, and pepper. Add the wing portions and stir to coat.
Grease a 7 x 11 baking dish. Pour in the wings and spread into an even layer.
Bake the wings for 30 minutes.
For the Sauce:
While the chicken is baking, in a different medium bowl, mix the green onions, sugar, ketchup, vinegar, soy sauce, and garlic powder and whisk together.
Place a medium sauce pan over medium heat and cook the sauce until thickened about 15 minutes.
When the chicken is done baking, pour the sauce evenly over the chicken stirring to coat.
Bake the chicken for another 5 minutes.
Transfer the wings to serving plates and top with the extra sauce from the baking dish.
Garnish with the chopped fresh parsley if desired.