Mix and mash the avocado, mayonnaise, dijon mustard, salt, black pepper, and hard-boiled egg yolks together.
Dice up the hard-boiled egg whites and the green onion.
Add the diced hard-boiled egg whites and green onion to the avocado-mayo mixture and mix.
Refrigerate for at least 30 minutes. Taste and add any additional salt, pepper, or dijon mustard.