Celery -Root Remoulade

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