2 celery hearts, finely chopped (about ⅓ cup)

¼ cup finely chopped red onion or shallot

1 tablespoon champagne vinegar

8 hard-boiled eggs, peeled and halved

2 tablespoons nonfat plain strained yogurt (Greek-style)

1 tablespoon yellow mustard

1 tablespoon mayonnaise

1 teaspoon chopped fresh dill, plus more for garnish

1 teaspoon chopped fresh chives, plus more for garnish

¼ teaspoon salt

¼ teaspoon ground pepper