01 -
Fill a large saucepan three-quarters full with cold water and bring to a boil over medium-high heat. Carefully lower eggs into the water and boil for 6 minutes 30 seconds for jammy yolks, or up to 8 minutes for soft-boiled.
02 -
Fill a large bowl halfway with ice and water. When eggs are cooked, immediately transfer to the ice bath and cool for about 8 minutes.
03 -
Gently peel cooled eggs and place them snugly in a flat container in a single layer.
04 -
In a large bowl, combine finely diced yellow onion, thinly sliced scallions, serrano pepper (if using), and garlic. Add soy sauce or tamari, water, granulated sugar, mirin, toasted sesame oil, toasted sesame seeds, and hondashi. Whisk until sugar is dissolved.
05 -
Pour the marinade over the eggs, ensuring they are fully covered. Top evenly with thinly sliced lemon.
06 -
Cover the container and refrigerate for at least 6 hours or overnight. Serve chilled or at room temperature over steamed white rice, with a spoonful of marinade if desired.