The Perfect Soft-Boiled Egg


The Egg is a most versatile ingredient. In itself, it packs the capacity of an entire meal and boasts the nuclear power of both mayonnaise and meringue. We’ve come to acknowledge the Power of the Egg and its indispensable stronghold within the kitchen larder. Just a couple of days ago I discovered another way of cooking eggs, a method that W came to know about when she was traveling in Japan some years ago.

Onsen Tamago, which translates literally to ‘Hot Spring Egg’ from Japanese, is traditionally prepared by lowering eggs in a basket into a hot spring, to cook slowly for forty minutes or so. This method – of cooking the egg at the magical temperature range of 65-70 degress Celsius – capitalises on the different cooking times of an egg white and yolk. Thus producing a silky smooth melt-in-your-mouth exterior white that envelops a creamy golden yolk. Think of it as something like the egg white of a poached egg with a yolk of a half-boiled egg, but better. It is the perfect soft-boiled egg.

Here’s how you can do it at home, if like us, you don’t have a natural hot spring at your disposal:

  1. With a pot on the hob, bring your water up to the optimum temperature range of 65-70 degrees Celsius. I’m afraid the only way to do it is with a kitchen thermometer, so simply stick it in and leave the guesswork aside.
  2. Subsequently, the key is to find a heat setting on your hob that allows it to maintain the water at that temperature range. This is very important.
  3. Lower the eggs into the pot gently and cook away for 40 minutes. Be sure to keep on eye on that thermometer, checking it from time to time, adjusting the heat accordingly to keep the eggs cooking in water that is 65-70 degrees Celsius.
  4. After 40 minutes, remove the eggs from the pot and plunge it into cold water to stop it from cooking further. When it is cool enough to handle, crack the shell open and gently release the egg into a serving bowl of warm bonito-soy sauce-water mixture. Having it simple with a small splash of soy sauce works fine as well!
  5. Devour demurely before the egg gets cold.


Onsen Tamago is a real hassle compared to speedy scrambled eggs, or easy fried eggs. But all you have to do is make it just once, and you’d understand completely what the hype here is all about. I know I badger W for a couple of these perfectly soft-boiled eggs ever too often.

And.. here’s the collectable recipe card!

Onsen Card

x, K


3 responses to “The Perfect Soft-Boiled Egg

    • Hi Charlie,
      it depends on the temperature of the water then. Essentially, you want to make sure the egg cooks throughout the 40 minutes at the temperature range of 65-70 degrees Celsius; this might mean you have to turn the heat on and off from time to time.


  1. Pingback: THE PERFECT SOFT-BOILED EGG | Small Potato·

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