Place the peeled hard‑boiled eggs on a cutting board and chop them into small pieces; transfer the chopped eggs to a large mixing bowl.
Add 1/3 cup plain Greek yogurt, 1 tablespoon Dijon mustard, 1/4 cup finely chopped celery, 1 tablespoon chopped chives, 1/4 teaspoon salt, and 1/4 teaspoon black pepper to the bowl with the eggs.
Gently fold the ingredients together with a spoon or rubber spatula until the mixture is evenly combined and the eggs reach your preferred texture.
Taste the egg salad and, if desired, adjust the seasoning with small additional amounts of the salt or pepper you already have.
Serve the egg salad on whole‑grain bread, in lettuce wraps, or as a side with your favorite greens.