In a saucepan, melt 2 tablespoons of the butter. Add the neck pieces, wing tips, heart and gizzard and cook over moderate heat until well-browned all over, about 10 minutes. Add the carrot, celery and onion and season with salt. Cook, stirring often, until the vegetables start to brown, about 5 minutes. Add the parsley stems, peppercorns, cloves, bay leaf and thyme and cook for 5 minutes longer. Add the chicken stock, water and wine and bring to a simmer. Skim the broth and reduce the heat to low. Cover partially and simmer until the giblets are very tender, about 2 hours.