Dry the chicken: Pat both sides of the chicken breasts dry, with a paper towel.
Prepare the spice rub: Whisk together the spice rub mixture in a small mixing bowl. Set aside.
1 ½ tsp Garlic Powder, 1 ½ tsp Onion powder, 1 tbsp Mustard powder, 2 tbsp Brown sugar, 1 tsp Smoked paprika, 1 tsp Cayenne pepper, 1 tsp Sea salt
Prepare the sauce: In another medium-sized mixing bowl, whisk together the ingredients for the Alabama white sauce. Keep covered and refrigerated until you are ready to serve.
½ cup Mayonnaise, 2 tsp Apple cider vinegar, 1 tsp Worcestershire sauce, 1 tsp Dijon mustard, 1 tbsp Prepared horseradish, ½ tsp Garlic Powder, 2 tsp Sugar, Salt and pepper to taste
Season the chicken: Liberally sprinkle the chicken breasts with the mixed spice rub, on both sides. Rub the spice mix into the chicken with your hands.
4 Chicken breasts
Preheat: Preheat your grill to 425°F, or a grill pan on medium-high heat. Spray the grill or grill pan with cooking spray.
Grill: Sear the chicken, skin-side down, for approximately 20 minutes on each side. If using a barbecue, you can keep the heat lower on one side of the barbecue, and transfer the chicken breasts to the cooler side to continue cooking. Cook the chicken until it reaches an internal temperature of 165°F on an instant read thermometer.
Brush with sauce: Finish the chicken by brushing with the white bbq sauce onto the hot chicken.