Gather all the ingredients.

Put 3 large eggs in a medium saucepan and add enough water to cover by 1 inch. Bring it to a boil on medium heat. Once boiling, cook for 12 minutes.

Once it’s finished cooking, transfer the eggs to iced water to stop the cooking. Let them cool completely and peel the eggshells.

Transfer the peeled eggs to a bowl and mash with a fork. Try to mash the egg whites into small, same-sized pieces.

Add ¼ teaspoon sugar and ¼ teaspoon Diamond Crystal kosher salt to the eggs.

Add ⅛ teaspoon freshly ground black pepper and 2 teaspoon milk.

Add 2 tablespoon Japanese Kewpie mayonnaise and mix very well. Taste and sprinkle more salt and pepper, if needed.

Set out 4 slices shokupan. Spread salted butter on top of each slice. For each sandwich, spread the egg salad on one of the slices.

Put the other slice of bread, buttered side down, on top of the egg salad. Place the sandwiches between two plates to compress slightly. Set aside for 5 minutes.

Cut the crusts off the bread. Repurpose them to make Shokupan Crust Rusks or freeze for later.

Cut the sandwiches in half. They’re now ready to serve.

You can keep any leftovers in an airtight container and store them in the refrigerator for up to 2 days.