01 -
Fill a large bowl with ice and water to create an ice bath.
02 -
Bring a medium pot of water to a boil, ensuring the water covers the eggs. Gently lower the eggs into boiling water using a ladle. Boil for 7 minutes for medium soft-boiled or 10 minutes for hard-boiled. After boiling, turn off heat and let eggs sit for 1 minute if soft-boiled.
03 -
Immediately transfer eggs into the ice bath and let them rest for 2 minutes to halt cooking. Remove while still warm and peel the shells.
04 -
Place peeled eggs in a large bowl and mash with a fork until pieces are smaller than a pea but not fully minced. Add sugar, salt, and pepper, continuing to mash. Optionally use a paring knife to refine texture.
05 -
Add Japanese mayonnaise and milk (if hard-boiled eggs are used) to the mashed eggs. Mix thoroughly and adjust seasoning if needed.
06 -
Spread 0.5 tablespoon of softened unsalted butter evenly over each slice of milk bread.
07 -
Spread egg salad evenly on one slice of bread. Top with the second slice, buttered side down. Press gently and trim off the crusts. Repeat for the second sandwich.
08 -
Optionally sprinkle sliced chives on top. Cut each sandwich in half and serve immediately.
09 -
Wrap sandwiches individually in plastic wrap and refrigerate for up to 2 days.