Ingredients

  • 3/4 cup well-shaken buttermilk
  • 2 teaspoons cornstarch
  • 1/2 teaspoon salt
  • Pinch of cayenne
  • 1 large egg yolk
  • 1 1/2 teaspoons extra-virgin olive oil
  • 1 tablespoon chopped fresh flat-leaf parsley
  • 1 tablespoon chopped fresh tarragon
  • 1 anchovy fillet, rinsed, dried, and finely chopped
  • 1 tablespoon chopped cornichon (French sour gherkin)
  • 1 tablespoon drained capers, rinsed
  • 1 teaspoon finely chopped shallot
  • 1/2 teaspoon Dijon mustard
  • 1/2 teaspoon sugar
  • 2 to 3 teaspoons fresh lemon juice
  • 2 tablespoons water
  • 1 (1-pound) celery root, peeled and coarsely shredded

Method

  • Whisk together 1/4 cup buttermilk, cornstarch, salt, and cayenne in a small heavy saucepan until smooth.
  • Whisk in yolk, then remaining 1/2cup buttermilk.
  • Cook over moderately low heat, whisking constantly, until mixture comes to a simmer and thickens, 4 to 5 minutes.
  • Transfer to a small bowl.
  • Whisk in oil, herbs, anchovy, cornichon, capers, shallot, mustard, sugar, lemon juice, and salt and pepper to taste.
  • Chill remoulade, covered, at least 30 minutes.
  • Whisk water into remoulade to thin and toss with celery root.