How to Make It
In a large pot, heat the oil over moderate heat. Add the onion, carrot, celery, and 1 teaspoon of the salt and cook, stirring occasionally, until the vegetables start to soften, about 10 minutes.
Add the chicken, potatoes, turnips, broth, vinegar, water, thyme, bay leaf, and the remaining 1 teaspoon salt. Cover and bring to a boil.
Reduce the heat and simmer, partially covered, until the chicken is just done, about 10 minutes for the breasts and 15 minutes for the legs and thighs; remove each piece as it is done.
Continue simmering the soup until the potatoes and turnips are tender, about 5 minutes longer. Stir in the pepper and parsley. Remove the thyme sprig and bay leaf. To serve, divide the chicken pieces among four shallow bowls and ladle the broth and vegetables over them.