Onsen Tamago (Hot Spring Egg)

Onsen Tamago (温泉卵 - Hot Spring Egg)

With an ethereal texture like silky smooth custard, Onsen Tamago or Hot Spring Egg is a Japanese egg dish named after how it was traditionally cooked in hot spring water. These slow cooked eggs can be eaten by themselves, but they're also used as a topping for other dishes in Japanese cooking. Since not all of us have hot springs in our backyards, I'm sharing three different cooking methods you can use to make these Japanese breakfast treats at home.

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• Onsen Tamago (温泉卵 - Hot Spring Egg)
• Why This Recipe Works?
• Ingredients for Onsen Tamago
• How to Make Onsen Eggs
• FAQ
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Why This Recipe Works?

• Making Onsen Tamago involves cooking the egg to a specific temperature (145° F or 63° C). I've detailed 3 methods you can use to achieve this.
• For the first method, you only need a pot and some measuring cups, but this method is the trickiest to get right.
• The second method uses the warming function of most modern rice cookers.
• The third method is the most reliable but requires a thermal circulator.
• You can serve Onsen Tamago with soy sauce, but making the dashi-based soy sauce will elevate your hot spring eggs to the next level. I also have a full recipe for Dashi Shoyu if you're interested in making this versatile condiment.

Ingredients for Onsen Tamago

• Eggs - I used large eggs for this. If you use other sizes, you may need to adjust the cooking time for Methods 1 and 2 (The cooking time is less important for Method 3). I also recommend using the freshest eggs you can find, as these will have less loose albumen than older eggs.
• Dashi - Dashi is a Japanese stock made with katsuobushi (dried, smoked, and fermented skipjack tuna) and konbu (kelp). You can use dashi packs, or I have a dashi making tutorial you can follow.
• Soy sauce - Any Japanese dark soy sauce (such as Kikkoman) will work. Remember that Chinese dark soy sauce is different from Japanese dark soy sauce.
• Salt - Using soy sauce alone to season the sauce will turn it dark brown. That's why I only use a little and then augment it with salt.
• Sugar - The sugar balances out the sauce's saltiness and is not enough to make it obviously sweet.
• Garnish - I prefer my onsen eggs without a garnish, but it's not very pretty. If you want to make it look better, you can garnish it with some chopped scallions or mitsuba.

How to Make Onsen Eggs

Below I show you how to make onsen egg at home using three methods. The first method requires the least special equipment but is the trickiest to get right. The second method uses an appliance that you probably already own. The third method requires a special machine, but it is the easiest and most reliable method.

Method 1: In a Pot

This onsen egg recipe doesn't require any special equipment, but it's also the most finicky and may require some experimentation to dial it in. In my testing, slight differences in variables such as the temperature of the tap water, the temperature of the eggs, or the thickness of the pot can make a big difference in the time it takes to get a perfect onsen tamago. This method is also the most time-sensitive, as a five-minute difference in cooking time can mean the difference between a raw egg yolk and a luscious custard-like yolk.

The key here is to use your heaviest pot, as it will retain heat the best. I also recommend using a thermometer to check the temperature of the water along the way for the most reliable results. Add 10 US cups of water to the pot and bring it to a rolling boil on the stove with the lid on.

Once the water is at a boil, turn off the heat and pour in 3 cups of tap water. This should bring the water temperature down to about 180°F. Next, add 5-8 cold eggs from the refrigerator, lowering the water temperature to just under 170°F. Cover the pot with the lid and set the timer for 20 minutes. Transfer the cooked eggs to an ice bath to stop carryover cooking.

Method 2: Rice Cooker

Modern rice cookers have a "keep warm" mode that typically keeps the pot at around 160° F (71° C). This is still above the ideal temperature of 145° F (63° C), but because it's actively heated, you can start with water close to the target temperature after adding the eggs. Then, the temperature will slowly rise from there. This gives you a little more leeway in terms of time. Using this method, I've generally found that you can leave the eggs in from 20-30 minutes and still have it turn out.

As far as getting the water to the ideal temperature, I usually use 5 US cups of boiling water to 1 ½ cups of tap water. Once added to a cold rice cooker pot with 5 cold eggs straight from the fridge, the water should be around the target temperature. Then you can turn on the keep warm function and set a timer for 25 minutes.

When the Onsen Tamago are done, transfer them to a ice bath to stop carryover cooking.

Method 3: Sous Vide Machine

Using an immersion circulator is the safest and most reliable way of making Onsen Tamago. Also known as a sous vide machine or thermal circulator, these devices consist of a heating element with a pump that holds a hot water bath at a precise temperature. This lets you cook food in the water bath to the exact temperature you want. For me, the perfect temperature for onsen eggs is 145° F (63° C). Once the hot water bath is up to temperature, just add the eggs and run the machine for 45 minutes. This will result in a soft custardy egg white with a thick egg yolk that's the texture of cold honey.

More Ways to Serve Onsen Tamago

These Hot Spring Eggs are delicious served as they are with a splash of dashi shoyu, but they also make a sumptuous garnish for ramen, udon, Japanese curry, donburi, or even a bowl of rice, or Soy Sauce Butter Rice. If you live in a country where eggs aren't safe to eat raw, cooking them this way will make them safer, and you can still enjoy the silky egg whites and rich, runny yolks dripping down and mingling with the dish.

Other Japanese Egg Recipes

• Teriyaki Eggs
• Chawanmushi
• Tamago Kake Gohan
• Tamagoyaki
• Dashimaki Tamago
• Usuyaki Tamago
• Ramen Egg

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