The Best Egg Salad Recipe for Sandwiches

Name: The Best Egg Salad Recipe for Sandwiches
Ingredients: 2 celery hearts, finely chopped (about 1/3 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, such as 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