Preheat oven to 325F/163C degrees. Set aside turkey and chicken. Melt 1 stick of butter in saucepan or microwave. Set aside.
FOR THE STUFFING:
Place breads in a large mixing bowl and set aside. Melt 1 stick of butter in large pan over medium heat. Saute celery, onions, and sage together until vegetables are cooked through. Add pepper. Transfer to mixing bowl with breads.
Using the same pan, add the sausage and break it up with a spoon as it browns. Add to the bowl with the bread/vegetable mixture and mix it all together thoroughly, adding chicken broth as needed to slightly moisten the mixture.
FOR THE TURCHICKEN:
Place deboned turkey skin side down on large cutting board surface. Spread ⅔ of stuffing on top of meat side of turkey. Place skinless, deboned chicken on top of stuffing, season chicken meat with salt and pepper, and spread with the remaining stuffing. Fold the sides of the turkey together so the chicken remains inside and begin trussing turkey starting at neck and moving down to tail. Tie to all together to resemble a whole turkey.
Place in large roasting pan on rack or without rack. Pour melted butter all over turkey surface. Season with salt and pepper. Sprinkle with the herbs, if desired.
Place in oven, on lower rack, and roast 3 ½ hours to 4 hours, basting every 45 minutes. Roast until middle of turchicken registers 165F/74C degrees.
Remove turchicken from oven, tent with foil, and allow to rest for at least 15 minutes. Slice turchicken horizontally to get whole slices containing turkey, chicken, and stuffing.