Place chicken breasts, one at a time, in a zip-top bag. Pound to an even thickness, being careful not to puncture the bag.

In a medium bowl, whisk together soy sauce, applesauce, onion, ginger, garlic, canola oil, bourbon, BBQ sauce, apple cider vinegar, brown sugar, and red pepper flakes.

Reserve 1/3 cup of the marinade. Pour the remaining marinade into the zip-top bag with the chicken. Marinate in the refrigerator for at least 30 minutes, or up to overnight.

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

Transfer the grilled chicken to a plate, tent with foil, and let rest while you make the sauce.

In a small saucepan, combine the reserved 1/3 cup marinade with the chicken broth. Bring to a boil over medium-high heat. Reduce heat to medium-low and simmer until the sauce has slightly thickened, about 5-6 minutes.

Slice the chicken breasts, drizzle with the bourbon sauce, and garnish with sliced scallions. Serve immediately.