Rinse the chicken in a bowl 2-3 times, then remove the water and add soy sauce. Mix sauce and let marinate for 15-30 mins.
Heat 1 tbsp oil in a skillet or wok on medium-high heat, then add ginger slices and saute for 2-3 mins, stirring occasionally. Add green onion whites and minced garlic, and cook for another 30 seconds.
Remove all of the aromatics, add another 1 tbsp oil and sautee chicken until lightly browned on both sides, about 4 mins. When removing chicken from marinating bowl, leave the soy sauce in the bowl for later, or the chicken will be too wet to brown properly.
Add back aromatics, as well as all of the coca cola, sugar, chili (if using) and soy sauce leftover from marination. Bring to a boil, reduce to medium heat, and wait till it reduces, about 20-30 mins depending on pan surface area. Stir occasionally. Skim off any darker impurities that rise to the surface during this process (white foam doesn’t need to be removed).
When there is not much liquid left (approx. half a cup or 125 ml) left, stir the pan constantly, until the liquid is thick enough to coat the wings. Remove from heat, mix in scallions, and serve.
