- 2 tablespoons lard
- 2–3 leeks, sliced into rounds
- 1–2 celery roots, peeled and cut into ¾-inch cubes
- 1 bouquet garni (an herb bundle tied with string) including a bay leaf and any or all of the following: a sprig of thyme, a sprig of sage, a sprig of parsley, a rosemary stem
- 1 quart chicken stock
- 1 cup yogurt, buttermilk, half-and-half, or whole milk (or ½ cup cream or crème fraiche)
- Salt and pepper to taste
- Crème fraîche or cream
- Finely minced rosemary, thyme, sage, or parsley leaves (or a combination of these herbs), or a grind of black pepper
Wash leeks by immersing in water, pulling apart, and agitating, then lifting them out of the water with your hands carefully, leaving the dirt behind.
Heat the lard in a medium-size soup pot. Add the leeks and sauté until tender. Add the celery root, chicken broth, ½ teaspoon salt, and a few grinds of black pepper. Add the bouquet garni and bring the pot to a boil. Cover the pot, reduce heat and simmer until the celery root is fork-tender.
Turn off the heat and remove the bouquet garni. Purée the soup with an immersion blender (or in a blender or food processor), adding the yogurt or other dairy, and more salt and pepper as you blend. Taste and adjust the seasonings.
Serve in a shallow bowl with a dollop of crème fraîche and a sprinkling of herbs or black pepper.