Onsen Tamago – Custardy Eggs in Broth

“Onsen” means “hot springs” and “tamago” means egg. These Japanese eggs were traditionally cooked directly in 140F hot springs for 45 minutes. You are literally creating custard in the shell.

This recipe uses a stove top, raises the temperature to 167F, and shortens the cooking time to 13 minutes. They’re served with a soy-dashi sauce/broth…  and they’re the eggs of my dreams. I used to eat them in the late 80s in Tokyo when I worked in a hostess bar until 4am. When the shift was over, the bartender would sometimes serve these to us…

You need a small pot, and an insta-read thermometer.


Eggs (4 – serves 2 people)



2 Tablespoons mirin

2 teaspoons sugar

1/2 cup soy sauce

Chopped green onions


To make the eggs:

Fill a small pot with cold water,  add the whole eggs (shell on) and slowly bring to 167F. Set the timer for 13 minutes. Cook on a low flame. You’ll need to adjust the heat as necessary to maintain the temperature.  This means checking with the thermometer every few minutes! (Small fluctuations of a degree or two up or down are fine.) Transfer eggs to an ice bath to stop them from cooking.

To make the broth:

  1. The kaeshi:  In a shallow pan, bring the mirin to a simmer, add the sugar and stir, add the soy sauce and stir.
  2. Make the dashi according to the recipe on the packet of granules, 1 teaspoon granules to 1 cup water.

To serve, carefully crack each egg and scoop it out.  Serve in a bowl over warmed leftover rice with a tablespoon of kaeshi, three tablespoons of dashi, and a sprinkling of green onions.