Cut the eggs in half, remove the yolks, and place them in a bowl. Finely chop the egg whites.
Mash the yolks with mayonnaise, mustard, salt, and pepper until smooth.
Stir in the chopped egg whites, green onion, and celery.
Serve on bread, in a wrap, or over a bed of lettuce.
Notes
Hard-Boiling Eggs: Place eggs in a pot, cover with water, and bring to a boil. Remove from heat, cover, and let sit for 15-17 minutes. Transfer to an ice bath for 5 minutes before peeling.
Storage: Keep leftover egg salad in an airtight container in the fridge for up to 4 days.