POTATO, PARSNIP, AND CELERY ROOT SOUP

Potato, Parsnip, and Celery Root Soup image

Yield Makes about 8 cups

Number Of Ingredients 16

1 tablespoon unsalted butter
1 tablespoon extra-virgin olive oil
2 large leeks, white and light green parts only, sliced
Kosher salt
2 large Yukon gold or other waxy potatoes (about 1 pound), peeled and diced
2 medium parsnips (about 8 ounces), peeled and diced
1 medium celery root (about 10 ounces), peeled and diced
2 large cloves garlic, chopped
1 teaspoon ground mustard
4 large sprigs thyme
1 bay leaf
1/4 cup dry white wine or dry vermouth
4 cups homemade vegetable broth (or low-sodium store-bought broth)
1 cup water
1/4 cup heavy cream (optional)
1 tablespoon freshly squeezed lemon juice, more as needed

Steps:

In a soup pot or large Dutch oven, heat the butter and oil over medium-low heat. Add the leeks and 1/2 teaspoon salt and cook, stirring occasionally, until soft and translucent, 6 to 8 minutes. Add the potatoes, parsnips, celery root, and garlic, cover the pot, and stir occasionally until the veggies are heated through and softening a bit on the edges, about 10 minutes. Add the mustard, thyme, and bay leaf and continue to cook for 2 more minutes, or until aromatic. Add the wine and cook until the liquid has completely evaporated, about 1 minute.
Add the broth and water, cover the pot partially, and increase the heat to medium-high. Bring just to a boil, then lower the heat to maintain a gentle simmer. Continue to cook, partially covered, until the vegetables are completely soft and have started to break down a bit, 45 minutes to 1 hour.
To finish the soup, remove and discard the thyme stems and bay leaf and, working in batches, carefully puree the soup in a blender (or use an immersion blender). If you prefer a thinner soup, add a little more water to adjust the thickness.
Stir in the cream and the lemon juice and taste. Adjust with more lemon juice or salt as needed and reheat as necessary.
tip
This soup is wonderful garnished with fresh croutons sautéed in butter and some chopped chives.