While the turkey roasts, melt the remaining 1 tablespoon of butter in a medium saucepan. Add the wing tips and neck pieces, season with salt and pepper and cook over moderate heat until browned, about 10 minutes. Add the onion and celery and cook until lightly browned. Sprinkle in 2 tablespoons of the flour and cook, stirring, for 1 minute. Slowly pour in the remaining 1/2 cup of wine and stir until smooth. Gradually stir in the turkey stock and bring to a boil. Cover and simmer over low heat until reduced to 3 1/2 cups, about 2 hours. Strain and set aside.