In this recipe, you butterfly the chicken before grilling it. The result is scrumptious with crisp skin, moist meat and an elegant presentation.
Prepare the grill.
Remove the giblets from the inside of the chicken. Place the chicken legs down (breast side facing up) on a cutting board. Cut along one side of the backbone, starting at the tail end and going up to the neck. Then cut the other side of the backbone, and remove it. Flip the chicken over, so the cut side is facing down. With the palm of your hand, press the breast down, flattening the chicken. Sprinkle kosher or sea salt and freshly ground pepper on the chicken. If you are not making the gravy, sprinkle on a teaspoon dry or fresh herbs of your choice. Insert two long metal skewers into the chicken cross-wise, underneath the legs, from one side of the breast to the other, about evenly spaced.
Place the chicken on the hot grill. Close the lid and leave the vent open. Cook the chicken for approximately 60 - 70 minutes, turning it over about halfway through. The chicken is ready when its juices run clear. If you have an instant read thermometer, that gives the most accurate measure of whether the meat is fully cooked. The internal temperature should be 165° F/74° C on an instant read thermometer stuck into the meat and not touching the bone.
After the chicken is done, let it rest for a few minutes before carving.
Simmer the giblets and backbone in 2 cups (16 oz./473 ml) of water with the rosemary for approximately 30-40 minutes. This creates a small amount of chicken stock that will be the base for the gravy.
In a small separate pan, melt the butter, add the flour and cook the flour for about 2 minutes, stirring constantly. Add a ladleful of the simmering stock into the butter and flour, then a bit more, until you have about ½ - ¾ cup (118-177 ml) of liquid in the mixture and it begins to thicken.
Throw out the giblets and backbone and add the flour/butter/stock to the rest of remaining stock. Add salt and pepper to taste. (Start with just a little and add only after tasting.) If you like a richer gravy, stir in the cream. Put a ladleful of the gravy in a small bowl and brush it onto the chicken during the last few minutes of cooking. Serve the rest of the gravy on the side.
These days we would call this recipe spatchcocked and grilled chicken. (The spatchcocking technique, basically cutting a chicken down the back then flattening or butterflying it, can also be used for roasting chicken in the oven.)
Although I have provided the directions for the gravy specified in the original recipe, the chicken is quite flavorful on its own.