Tamagoyaki Sandwich

Instructions

1. Prepare the egg mixture
   In a medium bowl, whisk together eggs, mirin, sugar, soy sauce, and salt until well combined but not overly frothy. Strain the mixture through a fine-mesh sieve to remove any large pieces of egg white for a smoother texture.
2. Cook the tamagoyaki
   Heat a rectangular tamagoyaki pan (or regular non-stick skillet) over medium heat. Lightly oil the surface. Pour a thin layer of egg mixture into the pan, tilting to cover the bottom evenly. When the egg is partially set but still slightly wet on top, begin rolling it from one end to the other. Move the rolled egg to the far side of the pan.
3. Continue rolling layers
   Add more oil if needed, then pour another thin layer of egg mixture into the empty part of the pan, lifting the rolled egg slightly to allow the new layer to flow underneath. When partially set, roll the first piece with the new layer. Repeat this process until all the egg mixture is used up.
4. Finish and cool
   Once all the egg mixture is used, remove the tamagoyaki from the pan and place it on a bamboo sushi mat if available. Roll it gently to shape it into a perfect rectangle. Let it cool for 5 minutes, then slice into 1/2-inch thick pieces.
5. Prepare the bread
   Lightly butter one side of each bread slice. Spread mayonnaise on the inside of the bread slices that will contain the egg.
6. Assemble the sandwiches
   Arrange the tamagoyaki slices on half of the bread slices. Sprinkle with chopped chives if using. Top with the remaining bread slices, mayonnaise side down. Gently press down to secure.
7. Trim and cut
   Using a sharp knife, cut off the crusts for an authentic Japanese sandwich appearance. Cut each sandwich diagonally into triangles or rectangles for serving.