Boil the eggs and let them cool.
Peel, then slice the eggs in half.
Remove the yolks and place them in a mixing bowl.
Chop the egg whites and add them to the bowl.
Add the Greek yogurt, chopped green onion, pickles, Dijon mustard, salt, pepper, onion powder, and mayonnaise (if using).
Mix until everything is well combined and creamy.
Spread the egg salad onto slices of high-protein white bread.
Cut the sandwich in half and enjoy!