1. Butterfly chicken by placing breast side down and using heavy-duty kitchen shears to cut along both sides of backbone. Discard backbone turn chicken over and open it like a book. Press gently to flatten it. 2. Place chicken in a large freezer bag. Add buttermilk 1/4 cup oil garlic peppercorns salt rosemary and honey. Seal bag securely and refrigerate overnight or up to two days. 3. Heat oven to 400 degrees. Remove chicken from marinade and place on a rack so excess can drip off. Line a roasting pan with foil and place chicken in pan. Drizzle with remaining 2 tablespoons oil. Roast for 45 minutes then reduce heat to 325 degrees. Continue roasting until well browned and until juices run clear when chicken is pierced where leg joins thigh about another 20 minutes. 4. Place chicken on a carving board and allow to rest for 10 minutes before cutting into serving pieces. Place a portion on each of four plates and drizzle each serving with pan juices.