Using sharp knife, cut through the back of the chicken, being careful to leave the breast intact.
The chicken is now spread open and, using a sharp filleting knife, remove the backbone and ribs, then carefully remove the bones from the breast. (It is vital that the skin of the chicken is not punctured or cut)
The legs and wings are left intact, de-boning of the interior of the body stopping at the first joint.
The bones can be used to make chicken stock that will make excellent gravy.
The interior of the chicken is filled by arranging first a layer of stuffing and then the additional chicken breasts.
Bring the cut edges of the back together and join with toothpicks, the toothpicks are ''laced'' together using the string. When most of the chicken has been re-assembled, you can add some extra stuffing (do not over-stuff!).
Now trim the toothpicks back to approx. 1" (2.5 cm) lengths with kitchen shears.
Place chicken on a rack in baking dish and arrange into shape, tie the legs together, and use string to hold chicken into correct appearance. Be sure to tie around the centre of the breast at least once, or the chicken will tend to split during roasting.
Bake at 325°F or 160°C, covered with foil for the first hour, and then continue to roast, basting frequently until internal temperature reaches 190 degrees F.
Allow to cool for 10 minutes or so, before serving.