Begin by taking your shokupan or soft white bread and gently removing the crusts from each slice. Set the crustless slices aside.

Hard-boil six large eggs by placing them in a pot filled with water, bring to a boil and cook for 9-12 minutes. Transfer them to an ice bath for 5 minutes, then peel carefully.

Cut the peeled eggs into quarters and place them in a food processor. Add Kewpie mayonnaise and pulse for 15-20 seconds until combined.

Transfer the egg salad mixture to a mixing bowl and season with salt and pepper to taste. If using scallions, chop them finely and fold them in.

Spread a layer of the egg salad mixture onto four slices of bread. Cover each slice right to the edges.

Carefully place the remaining slices on top to create a full sandwich, ensuring everything is evenly matched up.

Slice each sandwich in half diagonally and serve immediately or wrap them up for later.