In a pot of boiling water blanch garlic cloves for 30 seconds. Remove to ice bath to stop cooking. Remove skins
In a small bowl, combine softened butter, lemon zest, salt and pepper. Loosen the skin of the hens by slipping your fingers between the meat and skin of the breast and legs. Rub the butter mixture under the skin of each hen. Place a fresh sage leaf under the skin on each breast half and at each leg.
Place hens, head to toe, in roasting pan. Place garlic cloves inside the cavities and surrounding each hen.
Roast hens for 25 to 30 minutes at 400 degrees, until juices run clear when thigh is pierced.
Remove hens and garlic from roasting pan to platter. Pour off fat and juices into defatting cup. Place roasting pan over heat. Pour in 1/2 cup white wine to deglaze. Reduce until almost evaporated, scraping up the brown bits from the bottom of pan. When reduced, add 1 cup chicken stock and any juices that have settled in the defatting cup and from the platter. Mix together 2 tablespoons arrowroot and 2 tablespoons water. Add to sauce and bring to a boil to achieve full thickening power.
Cut hens in half down breast bone and back bone. Serve half a hen per guest. Serve pan sauce on side.