Hard-boil the eggs by placing them in a saucepan, covering with cold water, bringing to a rolling boil, then removing from heat and letting sit for 10-12 minutes before transferring to an ice bath.

Once cooled, peel the hard-boiled eggs and chop them into small, bite-sized pieces; transfer the chopped eggs to a mixing bowl.

To the chopped eggs, add mayonnaise, Dijon mustard, finely chopped celery, salt, and black pepper, then mix well until all ingredients are combined and the eggs are coated, adding chives if desired.