- In a glass dish, combine the buttermilk and spices. Add the chicken. Season with salt and pepper. Cover and refrigerate for 24 hours.
- In a large glass bowl, whisk together all of the ingredients. Cook in the microwave oven for 1 minute or until the sauce starts boiling. Set aside.
- Preheat the grill, setting the burners to medium. Oil the grate.
- Drain the chicken and pat dry slightly. Discard the marinade. Thread the chicken cubes onto flat metal skewers alternating with the green onions, if desired. Lightly oil the skewers.
- Grill the skewers for 5 minutes on each side. Brush the chicken with half of the barbecue sauce and grill for a minute longer on each side or until the chicken is cooked through. Set aside on a plate and tent with foil. Let sit for 5 minutes.
- Serve the chicken skewers with the remaining barbecue sauce. Serve with rice and green salad, if desired.