- 1 medium leek (white part only)
- 6 cups canned chicken broth or Chicken Stock
- 2 medium carrots (about 6 ounces), peeled and sliced ½ inch thick
- 2 medium parsnips (about 10 ounces), peeled and sliced ½ inch thick
- 2 small turnips (about 8 ounces), peeled, quartered, and sliced ½ inch thick
- 2 garlic cloves, sliced (about 2 teaspoons)
- 1 sprig rinsed and dried fresh thyme or 1 teaspoon dried
- 1 Turkish bay leaf
- 2 teaspoons extra virgin olive oil
- 1 pound beef flank steak
- Kosher salt and freshly milled black pepper
- 1/3 cup sour cream or creme fraiche
- 1 teaspoon prepared wasabi
- Halve the leek lengthwise and cut into ½-inch lengths. Soak (see Note). In a large saucepan, combine the leek with the broth, carrots, parsnips, turnips, garlic, thyme, and bay leaf. Bring to a boil over high heat;reduce the heat to low and simmer until the vegetables are tender, 15 to 18 minutes.
- Meanwhile, heat the oil in a large skillet over high heat until hot. Reduce the heat to medium-high and add the beef seasoned with salt and pepper. Sauté until well browned on both sides and medium-rare in the center, 8 to 10 minutes total. Remove the beef to a plate; cover loosely with aluminum foil and let rest 5 minutes, then slice thinly against the grain.
- Stir together the sour cream, any juices from the beef plate, and the wasabi; add salt and pepper to taste. Discard the thyme sprig and bay leaf; divide the vegetables and broth among 4 soup bowls. Arrange one-fourth of the beef in the center of each bowl and top each portion with a spoonful of the wasabi cream.