Creating a delicious Japanese Egg Sandwich is straightforward if you follow these steps:

1. Boil Eggs: Place the eggs in a pot of cold water. Bring to a boil over medium heat. Once boiling, cover and remove from heat. Let sit for 10-12 minutes.
2. Cool Eggs: After resting, transfer eggs to an ice bath to cool. Once cool, peel the eggs.
3. Mash Eggs: In a bowl, mash the boiled eggs with a fork until they reach your desired consistency—smooth or slightly chunky.
4. Add Condiments: Mix in mayonnaise, Dijon mustard, salt, and pepper. Adjust seasoning according to your taste.
5. Prepare Bread: Lay out the slices of bread on a clean surface. If desired, lightly toast them for extra texture.
6. Assemble Sandwich: Spread the egg mixture evenly on one slice of bread. If using, layer fresh lettuce leaves on top.
7. Complete the Sandwich: Place a second slice of bread on top and press gently.
8. Cut Sandwich: Slice the sandwich in half or quarters for a neat presentation.
9. Enjoy Immediately: Serve while fresh and enjoy the amazing flavors!

These steps will help you make an incredible Japanese Egg Sandwich that you’ll want to replicate time and again.