In a large stockpot, heat the olive oil over medium heat. Add the onion, half the carrots, the celery, bay leaves and garlic. Sauté for 4-5 minutes, taking care not to brown the garlic. Add the lentils, 2 tablespoons of the parsley, celery root and salt to taste. Add the stock, raise the heat to high and bring to a boil. Lower the heat and simmer, stirring occasionally, until the lentils are tender, about 35 minutes. Add the remaining carrots during the last 10 minutes of cooking. There may be an excess of liquid. If so, ladle it out and save it for anther use. (It is very flavorful and would be good in soup.) Add the walnut oil, remaining parsley and vinegar to the pot. Check the seasonings and finish with plenty of black pepper.