Hard boil the eggs by placing them in a pot of cold water, bringing it to a boil, then covering and letting sit for 10 minutes. Cool in ice water and peel.

In a mixing bowl, mash the hard-boiled eggs with a fork until chunky.

Add mayonnaise, Dijon mustard, soy sauce, sugar, green onions, salt, and pepper. Mix until well combined.

Butter one side of each slice of bread (optional) and toast them in a skillet until golden brown.

Spread the egg salad mixture evenly over half of the toasted bread slices.

Top with the remaining bread slices, cut in half, and serve.