Place your eggs in a medium-sized pot and cover with a few centimetres of cold water. When the water comes to a boil, turn off the heat. Cover the pot and let the eggs cook for 10 minutes.

Immediately transfer the cooked eggs to an ice bath for 14 minutes to stop the cooking process and cool them down.

Peel the eggs and separate the whites from the yolks.

On a cutting board, chop up the egg whites.

In a small mixing bowl, use a fork to mash the egg yolks.

Add the egg whites, Japanese mayonnaise, water, sugar, salt, and pepper in with the yolks. Mix together until everything is well blended.

Use softened butter to butter two slices of bread.

Pile the egg mixture into the centre of a slice of bread to help prevent it from spilling out the sides. Place the other slice of bread on top. If you are making this sandwich ahead of time, you may wish to wrap it in plastic wrap and store in the fridge with the crusts on.

When you are ready to enjoy, simply cut the crusts off of the sandwich and slice it in half.