1 medium celery root (about 1 lb), peeled, diced, and held in cold water with a squeeze of lemon juice
6 large potatoes (about 2 lbs), peeled and quartered
6 leeks (about 1 lb), rinsed and sliced
3 qts chicken or vegetable stock
Small bay leaf
Salt and freshly ground black pepper
1 cup crème fraiche or cream
1/2 cup plain yogurt or whole milk
1/2 cup chopped fresh herbs (parsley with a pinch of rosemary leaves in the winter; chives and tarragon in warmer months)
1. Put the celery root, potatoes, and leeks in a large pot with the stock over medium-high heat. Bring to a boil, add bay leaf, salt and pepper, and simmer over lowest heat until just before the vegetables are falling apart.
2. Remove the bay leaf and allow the soup to cool slightly before puréeing in a blender or passing through a food mill.
3. Put the soup back in the pot and, on low heat, whisk in the crème fraiche or cream and the yogurt or milk. Heat through, then stir in the fresh herbs. If you prefer a thinner consistency, add a bit more milk. Season to taste with additional salt and pepper.
Makes 10 to 12 servings plus some for the freezer