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

Bring the water to a boil over medium-high heat. Once boiling, cover the saucepan and turn off the heat. Let the eggs sit in the hot water for 10 minutes.

After 10 minutes, transfer the eggs to an ice bath to cool completely.

Peel the eggs and set aside.

Separate the egg yolks from the egg whites. Add the egg yolks to a bowl and the egg whites to a chopping board.

In the bowl with the egg yolks, add the Japanese mayo, salt, black pepper, sugar, and cream or milk. Mash the yolks and mix it all together until you have the consistency of a thick sauce or paste.

Chop the egg whites into small pieces and add then add them into the bowl with the egg yolks mixture. Combine all together.

Taste and adjust seasoning if needed.

Spread a thin layer of softened butter on one side of each bread slice.

Divide the egg salad evenly between the two slices of bread. Spread the egg salad to cover the entire slice evenly.

Place the remaining slices of bread, buttered side down, on top of the egg salad to form a sandwich.

For an authentic presentation, trim the crusts off the sandwiches. Cut each sandwich into halves or quarters, depending on your preference.

Serve immediately and enjoy your Japanese egg salad sandwich!