In a bowl, mix soy sauce, apple sauce, onion, ginger, garlic, oil, bourbon, BBQ sauce, vinegar, brown sugar, and red pepper flakes to create the marinade.

Marinate the chicken with the mixture for at least 30 minutes, preferably overnight.

Preheat the grill to medium-high heat. Remove chicken from marinade and discard excess marinade. Grill chicken for 4-5 minutes per side or until cooked through.

While grilling, pour remaining marinade into a small saucepan, add chicken broth, and simmer until slightly thickened, about 5 minutes.

Let the chicken rest for 5 minutes, then slice and serve topped with the bourbon glaze and sliced scallions.