Place the cold eggs in a medium saucepan and cover completely with warm water.

Bring the eggs to a rolling boil then quickly turn the heat down to a gentle simmer. Simmer the eggs for 10 minutes.

Once the eggs are done cooking, quickly remove from the boiling water and plunge the eggs into a bowl of ice water.

Crack eggs slightly after 5 minutes wait time, then leave them to sit in the cold water for the remaining 10 minutes. Or crack then peel the cold eggs under running water.

Separate the yolks from the whites and whip the yolks with the Kewpie mayonnaise, salt, sugar, and a pinch of freshly ground black pepper for seasoning.

Chop the cooked egg whites into small cubes and fold them into the creamy yolk mixture.

Lay four slices of shokupan bread on a cutting board. Use a sharp knife to slice off the bread crusts.

Butter the bread with soft salted butter and spread a thick layer of egg salad onto two of the bread slices. If adding a soft boiled egg, spread a thin layer on each side, slice the egg in half, and place in the middle of one slice of bread. Top with the other slice.

Top with the remaining buttered bread slices and slice the sandwiches diagonally.