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.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.