These flavorful soft-boiled eggs used as a ramen topping are called Ajitsuke Tamago (味付け卵) in Japan, which literally means "seasoned egg." This White Ramen Egg is marinated in a clear broth making it look like a regular soft-boiled egg and yet it has the perfect savory-sweet balance with loads of umami.
To make the brine, add the water, sake, sugar, and salt to a pot and bring to a boil. Continue boiling until the vapor no longer smells like alcohol.
Remove the pot from the heat and chill to room temperature.
Put the peeled eggs in a freezer bag and add the brine. Seal the bag, pressing out as much air as possible and refrigerate the eggs for at least overnight or up to 2 days.
If you want to keep them longer, remove the eggs from the brine after 2 days. Store them in a sealed container in the refrigerator for up to another 2 days.