KitchenTigress: Hot Spring Eggs (Onsen Tamago)

Hot Spring Eggs (Onsen Tamago)

Hot spring eggs (onsen tamago) are Japanese soft-boiled eggs. Japanese like to make them in hot springs, hence the namesake. When you break a hot spring egg, a solid egg falls out of the shell. You might think it's hard-boiled but it's very soft, and the yolk in the middle is still liquid.

Hot spring eggs may be eaten as a topping on rice. Or with some soba sauce and a sprinkle of spring onions.

If you have an easy way to keep water at 64ºC, making hot spring eggs is easy.

I use a rice cooker that has extended keep warm function.

You could also use a sous vide machine. Or a rice cooker or multi cooker that has temperature control.

What if you don't have an appliance that keeps water at a constant temperature?

You could monitor the water with a thermometer. Add some boiling water whenever the temperature dips. This is workable if you don't mind staying by the pot whilst the eggs cook.

What if you don't have a thermometer? Can you mix boiling and cold water in a pot, put your eggs in the water, set your timer, and walk away?

This method is a bit hit-or-miss. How cold is your cold water? How many eggs are you cooking? How well does your pot retain heat? All these factors affect the temperature of the cooking water. If you don't know what the temperature is, you're just stabbing in the dark.

What are the rewards for making onsen tamago successfully?

I love how the egg falls out of the shell, in one piece. One moment it's in the shell. The next moment it's sitting in the bowl, looking so pretty. I always take a few moments to marvel at how soft and smooth the egg white is.

I almost can't bear to eat the egg. It's such a feast for the eyes. But eat it I must for the smooth and creamy egg is also a feast for the mouth. When I break the yolk, there's a beautiful contrast of colours. Unfortunately, the small feast is gone in a flash.

How to make hot spring eggs

Step-by-step guide

This recipe uses a rice cooker with water held at extended keep warm function. The hot water bath is perfect for making hot spring eggs.

hot spring eggs
  • 1 egg, 65-70 g, cold
  • 1 tsp soba sauce
  • 2 tsp hot water
  • spring onions to taste, sliced
  1. Place cold egg in rice cooker. Add 30ºC water to cover 40% of egg. Add 100ºC water till egg is just totally submerged. Cover rice cooker. Select extended keep warm function. Cook egg for 1 hour.

  2. Place soba sauce in a bowl. Add hot water. Stir thoroughly.

  3. Crack egg into sauce. Sprinkle with spring onions. Serve immediately.