Ingredients

3 teaspoons whole-grain mustard

3 tablespoons fresh lemon juice

1/4 cup extra-virgin olive oil

Coarse salt and freshly ground pepper

1 medium celery root, peeled into ribbons (6 cups)

1 red onion, thinly sliced

2 ounces smoked mackerel, flaked

1/4 cup chopped fresh parsley

Preparation

Combine mustard and lemon juice. Add oil in a slow, steady stream, whisking constantly, until combined. Season with salt and pepper.

Toss dressing with remaining ingredients.