COOK IT.
In a medium bowl, whisk together the mayonnaise, sour cream, apple cider vinegar, brown sugar, spicy brown mustard, horseradish, lemon juice, salt, cayenne and white pepper. Mix until fully combined, then set aside.
Place chicken leg quarters on a sheet tray lined with aluminum foil. Gently pull away the skin from the chicken leg quarters, then drizzle inside and out with olive oil. Season the chicken leg quarters all over and under the skin with Pit Boss Chicken & Poultry Rub. Let chicken sit out at room temperature for 1 hour.
Fire up your Pit Boss grill and preheat to 450°F with the Sear Slide open. If using a gas or charcoal grill, set it up for medium-high heat and direct heat.
Sear the leg quarters on all sides over direct flame until crispy and golden brown. Transfer to indirect heat and close the sear slide. Reduce temperature to 350°F and grill the chicken for 45 minutes, turning occasionally, until chicken registers an internal temperature of 165° F.
Remove chicken from grill and allow to rest for 10 minutes. Serve chicken hot with a generous drizzling of Alabama white sauce*.