Spicy Barbecue Chicken

For Barbecue Mop Sauce:

In a nonreactive bowl bowl, combine vinegar, salt, pepper and pepper flakes; whisk until salt dissolves. Stir in the diced onion and diced chili pepper. Check seasoning; adding black pepper and red pepper flakes as needed. Set aside until chicken is ready to grill.

For Chicken:

Remove any packed giblets in the chicken cavity and remove any fat deposits just inside the body and neck cavities. You will need a sturdy pair of kitchen shears. Place the chicken, breast-side-down, on a cutting board. Using the shears, cut away the backbone and discard it. Then, flip the chicken over and press down to flatten it. Rinse the chicken inside and out under cold running water, drain and pat dry with paper towels. Set aside.

Prepare the grill for direct grilling. Preheat to medium. Lightly brush the grill grate with oil.

Arrange the chicken on the hot grate. Grill, skin side down, directly over medium heat, until grill marks form and the skin starts to turn color. If flare-ups occur move the chicken away from the flames to keep from burning. Grill for 10 to 12 minutes, the skin should be golden brown and crisp. Turn the chicken over and generously mop the grilled side of the chicken with sauce. Grill the bone side of the chicken for another 10 to 12 minutes, or until the chicken is cooked through. Reposition the halves occasionally so they cook evenly, mopping with sauce once the outside skin is crispy and cooked.