Ingredients

  • 2 tablespoons vegetable oil
  • 1 1/2 pounds skin-on, bone-in chicken thighs
  • Kosher salt, freshly ground pepper
  • 8 medium carrots (about 1 lb.), peeled, cut into 2" pieces
  • 1 small celery root (about 12 ounces), peeled, cut into 1/2" pieces
  • 1 medium onion, chopped
  • 1 leek, white and pale-green parts only, chopped
  • 1/4 cup (1/2 stick) unsalted butter
  • 1/4 cup all-purpose flour
  • 1 cup dry white wine
  • 4 cups low-sodium chicken broth
  • 4 sprigs thyme
  • 1 sprig rosemary
  • 2 bay leaves
  • 1 1/2 teaspoons (or more) Sherry vinegar
  • 2 1/4 cups all-purpose flour plus more
  • 2 teaspoons kosher salt
  • 3/4 teaspoon baking powder
  • 1/2 cup (1 stick) cold unsalted butter, cut into 1/2" cubes
  • 3/4 cup buttermilk
  • 2 tablespoons creme fraiche or sour cream
  • 2 tablespoons chopped fresh chives
  • 1 large egg, beaten to blend

Method

  • Preheat oven to 400°F. Heat oil in a large pot over medium-high heat. Season chicken with salt and pepper. Cook skin side down until skin is golden, 8-10 minutes; transfer to a plate.
  • Carefully drain all but 2 tablespoons fat from pot. Add carrots, celery root, onion, and leek; stir frequently until softened and beginning to brown, 8-10 minutes.
  • Add butter; stir until melted. Add flour and stir constantly until well blended, about 2 minutes. Add wine and 1/2 cup water. Bring to a boil; reduce heat and simmer until liquid is reduced by half, 5-8 minutes.
  • Add chicken, broth, thyme, rosemary, and bay leaves. Bring to a boil; reduce heat. Simmer until chicken is fork-tender, 35-40 minutes. Transfer chicken to a plate. Let cool slightly; shred meat, discarding skin and bones.
  • Return shredded chicken to soup. Add 1 1/2 teaspoons vinegar. Season with salt, pepper, and more vinegar, if desired. DO AHEAD:
  • Whisk flour, salt, and baking powder in a large bowl. Add butter. Using your fingertips, blend until pea-size lumps form. Add buttermilk, creme fraiche, and chives. Using a fork, mix until just combined. Gather mixture into a ball and knead in bowl just until a shaggy dough forms, 3 or 4 times.
  • Transfer dough to a floured work surface and pat into a 3/4"- to 1"-thick round. Cut out rounds with a 2" biscuit cutter or small glass. Gather dough and repeat patting and cutting. Transfer to a parchment-lined rimmed baking sheet; brush with egg.
  • Bake biscuits until golden brown, 25-30 minutes. Serve warm or at room temperature. DO AHEAD:
  • Divide soup among bowls and top with biscuits.