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I tried this just now and this is the only method I’ve tried that WORKS and didn’t break my straight from the fridge eggs when I added them to the hot water. Thanks so much for sharing! Now I can make perfect onsen tamago everydayyyy
★★★★★
– yakiimotional (from Instagram)
In Japan, you can buy a gadget made just for onsen eggs. But a pot, some water, and a thermometer will get you the very same egg.
Crack one into a small bowl and the cloudy white slides loose around a thick, jammy yolk. Think of a soft-boiled egg with the firmness flipped, the white softer than the yolk.
Onsen tamago
Recipe Snapshot
- What is it? Onsen tamago are Japanese-style eggs warmed slowly in their shells below boiling until the yolk is jammy and the white still loose, then cracked into a bowl with dashi sauce.
- Flavor profile: You taste the white first, cloudy to look at yet loose enough to slip across your tongue. Then the thick yolk clings, and the rich egg flavor lingers.
- Why this recipe works: Fridge-cold water and eggs mean the same starting temperature every time. A 3-minute rest finishes them, and ice water stops the heat before the white sets. I tested every number.
- How to make it: A lidded pot, a thermometer, a timer. Boil water, then kill the heat. Add chilled water, lower in the eggs, cover, and wait off the stove. Microwave the sauce.
- What to expect: The process takes about 25 minutes from the time the pot is placed on the heat. The eggs spend 15 minutes in the pot. They spend 10 minutes cooling. Time the 15 minutes and the 3-minute rest, and check the water with a thermometer once the eggs are in. Those numbers decide the egg.
What Is Onsen Tamago (Hot Spring Eggs)?
Onsen tamago, or ontama, is a Japanese-style egg eaten by the spoonful, jammy yolk and loose white. Crack it straight into a small bowl and pour dashi sauce over. It tops gyudon and udon and sits on ryokan breakfast trays, a truly versatile egg.
Yolk and white set at different temperatures. The yolk starts near 65°C (149°F) and turns jammy near 70°C (158°F). The white sets fully near 80°C (176°F). Hold an egg in that gap and the yolk firms first. The name is literal. Hot spring water sits in this range, and a home pot copies only its heat.
More than one egg goes by this name. At Umi Jigoku in Beppu, eggs hang from a bamboo pole in water at about 98°C (208°F). In Kannawa and Myoban, they steam over jigoku-gama, the hell cauldrons. Owakudani in Hakone hard-boils its kuro-tamago in a hot spring pool, and only the shell turns black. Inside, it is white. All are hot spring eggs, yet none is cooked low enough to set the yolk first, and a home pot never blackens a shell. The silky store-bought ontama in supermarkets and convenience stores is another thing again. Most are factory eggs pasteurized in the shell, with a half-set white and a near-raw yolk, and their makers class them separately from the old-style egg with its jammy yolk. If that store egg is your benchmark, this yolk may seem too firm. You did not overcook it. You are comparing a different kind of egg.
The name is said to come from hot spring ryokan that served these eggs at the table. An egg left in the spring water came out just like this, or so the story goes. Nobody knows when or where it started. Some towns did turn the name into a local product. Iizaka Onsen in Fukushima, where radium was first confirmed in Japan in 1910, saw its onsen tamago catch on as radium eggs around 1920. Onogawa Onsen in Yamagata sells a souvenir by the same name. When onsen tamago still turn up at a ryokan breakfast today, they carry on that local specialty.
The white turns cloudy and still flows because it is made of more than one protein. Ovotransferrin moves first. At about 61°C (142°F) it changes shape and clouds the white. Ovalbumin, most of the white, only joins in at higher heat, so the white stays cloudy and loose. A few degrees open the gap. In 65°C (149°F) water the white still flows after 3.5 hours. At 70°C (158°F) it stops flowing in 30 minutes. Stopping is a different thing from setting fully, which takes higher heat still.
The onsen tamago you see in most Japanese homes goes like this. Turn off the boiling water, add tap water, lower in the eggs, cover, and wait. You will also hear that eggs should come to room temperature first. My version steps away from that. I chill the added water in the fridge, and the eggs go in straight from the fridge too. Once out, they skip the cold water at first. They sit at room temperature while the leftover heat finishes them, and then ice water stops them. I changed it for one reason, so it never fails on you.
Onsen Egg Ingredients
- Eggs: Use them cold, straight from the fridge. Cold eggs help bring the water temperature down too, and eggs brought to room temperature will overcook. I use Japanese medium eggs, a size that counts as large to extra large in the US and medium in the EU. Then there is the egg itself. Use pasteurized eggs. Cooked in the shell at a low temperature, these eggs never reach 71°C (160°F), the safe internal temperature the US sets for eggs.
- Water: The water you boil, plus chilled water added once it boils. Chill that to about 10°C (50°F) in the fridge with no ice, since the ice water at the end has another job. Tap water is fine for boiling. Water hardness shows up in dashi and tea instead. This water only carries heat, so it needs no salt or vinegar.
- Ice water: Use water with ice floating in it. The 3-minute rest at room temperature (5 minutes in winter) lets the carryover heat finish the eggs. If that heat keeps going, the white sets too.
Substitutions & How to Customize
Everything that goes into the sauce can be rebuilt from what you already have in the kitchen.
Substitutions:
- Dashi sauce → Store-bought tsuyu or mentsuyu: Instead of mixing dashi, Japanese light soy sauce (usukuchi) and mirin yourself, a bottle of tsuyu, the Japanese noodle sauce, is fine. Dilute a concentrated one with water as the label says, then go a little weaker still. Straight mentsuyu, the ready-to-use kind, goes on just as it is.
- Dashi, light soy sauce and mirin → Shiro dashi: My second pick after store-bought tsuyu. Shiro dashi is kombu and bonito dashi already blended with light soy sauce and mirin in one bottle, so the sauce stays pale. Strength varies from product to product, so dilute it as the label says.
- Dashi → Dashi from a dashi packet: You do not need to make dashi from scratch. Dashi brewed from a dashi packet does the same job.
- Light soy sauce → Standard Japanese soy sauce: Use the same amount. The sauce turns darker and tastes a touch less salty.
How to Customize:
- Wasabi: Stir a little into the sauce. It goes well with both the egg and the sauce.
- Shichimi togarashi: Shake this Japanese chili spice blend on just before you eat.
- Yuzu kosho: A tiny dab of this yuzu chili paste on top brings up the yuzu aroma and a little heat.
- Toasted sesame oil: A few drops add a toasty aroma.
- Green onions or mitsuba: Chop either one, green onions or mitsuba (a Japanese herb), and scatter it over the top.
How to Make My Japanese Onsen Eggs
If you prefer to watch the process in action, check out my YouTube video of this recipe for a complete visual walkthrough!
Before you start (Mise en place):
- Put the water you will add later in the fridge and chill it to about 10°C/50°F.
To develop this recipe, I used a 20 cm stainless steel yukihira pan.
i. Pour the water into a lidded pot big enough to keep the eggs fully underwater.
Note: I worked out my numbers in an ordinary stainless steel pot (20cm).
ii. Cover and bring it to a full rolling boil. With the lid on, it boils faster.
i. Once the water is boiling hard, turn off the heat and pour in the chilled water.
ii. Right away, set the eggs straight from the fridge on a slotted spoon and lower them gently to the bottom of the pot, one at a time.
Drop them in and they hit the bottom of the pot and crack.
iii. Check the water with a thermometer. It will be at about 80°C/176°F by now.
iv. Cover, move the pot off the stove and set a timer for 15 minutes. Keep the lid on the whole time.
80°C is near where the white sets firm, but under the lid the water keeps cooling, and the eggs pass slowly through it. The white sits at 80°C only for the first few minutes. The yolk sets lower, so it still gets there and turns jammy before the white does. The cooling curve (volume, temperature, time) decides the result, so every number is fixed.
i. When the timer goes off, lift the eggs into a bowl and leave them at room temperature for exactly 3 minutes, 5 in winter. Time this one too.
The heat left inside the shell keeps cooking them slowly.
ii. While you wait, set up a bowl of water with ice floating in it.
iii. When the time is up, pour the ice water over the eggs in their bowl and chill them for 5-10 minutes.
This way, the egg slides cleanly out of the shell when you crack it.
i. Combine the dashi, light soy sauce, mirin and water in a small microwave-safe bowl, and microwave it uncovered at 600W for 1 minute.
That minute cooks off the alcohol in the mirin. Serve the sauce warm or let it cool first, whichever you like.
ii. Without peeling, crack each egg into its own small bowl.
iii. Pour the sauce over and scoop it up with a spoon.
Tips for the Best Onsen Tamago
- Measure the water and the temperatures, every single time. Measure the boiling water and the chilled water exactly. Then use a thermometer to check the chilled water at about 10°C/50°F and the water at about 80°C/176°F once the eggs are in. Measure loosely and the same steps give you a different egg from one day to the next. Check before the lid goes on, while a number that is off can still be fixed.
- Bring the water to a full rolling boil in the pot. About 80°C/176°F is what you get when the chilled water goes into water that has boiled hard. Leave the kettle and the microwave out of it, boil the water in the pot itself, and only then turn off the heat.
- Set out the lid, the timer and the thermometer before the water boils. Once the heat is off, the chilled water, the eggs, the thermometer and the lid follow one after another with no pause. Get the slotted spoon out now too, for lowering the eggs.
- Cook no more than 4 eggs at a time. Cold eggs pull the water temperature down, so every extra egg leaves the water colder, until it is too cold to do its job. If you need more, run the same steps in a second pot alongside.
You cannot see inside the shell until you crack it, so how this egg turns out comes down to the numbers on your thermometer and your timer.
Storage & Meal Prep
Fridge: Keep them in the shell and eat by the next day. Unlike factory-made ones, eat any cracked ones right away.
Freezer: You cannot freeze onsen tamago.
Meal prep: Supermarket and convenience-store ones keep, so it is easy to assume yours will. Homemade is not for make-ahead. Make only what you will eat within a day.
What to Serve With Hot Spring Eggs
- Stovetop Japanese Rice
- Classic Dashi Miso Soup
- Shiozake (Salted Breakfast Salmon)
- Natto (Fermented Soybeans)
Onsen Egg Troubleshooting
Most often, an egg knocks hard against the bottom of the pot and the tiny crack it gets spreads in the hot water. Shells vary in hardness from egg to egg, and a just-laid egg can even crack from the gas inside it. Set each remaining egg on a slotted spoon and lower it gently all the way to the bottom. Eat any cracked egg as soon as it is done.
Either the heat went off before the water had boiled hard, or the amount of water or the temperature of the chilled water drifted from the numbers. Until the lid goes on, you can still bring it back. Add a little at a time, cold water if it runs hot and hot water if it runs cool, then cover once the thermometer reads about 80°C/176°F.
A white that set all the way means the egg got too much heat somewhere along the line. Usually the water was hotter than about 80°C/176°F after the eggs went in, the eggs had been brought to room temperature, the rest on the counter ran past 3 minutes (5 in winter), or they were cooled in cold water instead of ice water. Eat that batch as soft-boiled eggs. Next time, confirm about 80°C with the thermometer and keep the room-temperature rest on a timer.
A white that is still nearly clear and watery needs more heat. Usually the water was cooler than about 80°C/176°F after the eggs went in, the lid came off partway through, or the eggs came out before the 15 minutes were up. If the first one you crack looks like this, return the rest, still in their shells, to water brought to 65-70°C/149-158°F on the thermometer, and give them a few more minutes.
The white is so loose that cracking the egg one-handed over the bowl of sauce sends the yolk skidding sideways and the white splashing out. For the rest, pull each shell apart top and bottom over a separate small bowl, then slide the egg gently from there into the bowl of sauce.
More Japanese Egg Recipes
If you like steering how an egg sets with temperature, chawanmushi and egg drop soup play the same game, and you will find the rest in my Japanese Egg Dishes.
Did You Try This Recipe?
I would love to hear your thoughts!
💬 Leave a review and ⭐️ rating in the comments below. 📷 I also love to see your photos – submit them here!
Onsen Tamago (Japanese Hot Spring Eggs)
Ingredients
- 4 eggs chilled & straight from the fridge, pasteurized
- 1500 ml water
- 300 ml cold water chilled in the fridge
- ice cold water
- 2 tbsp dashi stock liquid not powder
- ½ tbsp Japanese light soy sauce (usukuchi shoyu)
- 1 tbsp mirin
- 1 tbsp water
The ingredient brands and tools I trust are in my Japanese pantry guide and my cooking tools guide.
Can’t find certain Japanese ingredients? See my substitution guide here.
Instructions
- Measure out 300 ml cold water and place it in the refrigerator. It should be fully chilled before you start (about 10°C/50°F). Once chilled, add 1500 ml water to a pot and bring to a rolling boil. (Tip: Heating with a lid will speed up the process.)
- Once the water is thoroughly boiling, turn off heat and add the cold water from the fridge.
- Immediately add 4 eggs straight from the fridge. At this point the water should be about 80 °C (176 °F).
- Cover, move the pot off the stove and set a timer for 15 minutes. Keep the lid on the whole time.
- Remove the eggs and rest in a bowl at room temperature for exactly 3 minutes (5 minutes in winter). Use a timer to ensure accuracy. While you wait, prepare a bowl of ice cold water.
- Once rested at room temperature, pour ice-cold water into the bowl to halt the cooking process and stop them from cooking any further. Rest for 5-10 minutes, this will help them come out cleanly before serving.
- Combine 2 tbsp dashi stock, ½ tbsp Japanese light soy sauce (usukuchi shoyu), 1 tbsp mirin and 1 tbsp water in a small microwavable bowl. Microwave uncovered for 1 minute at 600W. The sauce can be served warm or cooled depending on preference
- Crack the egg into a serving bowl and add about 1 tbsp of sauce for each serving. Enjoy!
Hello Yuto, I really like your recipes. I am going to try this one with a poach eggs. More simple forme me. I’m an old lady who love Japanese food and sometimes try short cut.
Thank you for recipes.Sorry for some of my adaptation, wish you the best.
Hi francine,
Thank you for your comment!
There’s absolutely no need to apologize! I only share these Japanese recipes as inspiration, and I’m always happy when my readers make them your own. I believe adapting dishes to suit your preferences and what’s available to you is part of the joy of cooking.
And warm comments like yours is incredibly encouraging and motivates me to continue developing new recipes. I truly appreciate your support!
Yuto
Aloha Yuto-san, I saw the video on IG and it led me to this page, which I was very excited to find. I typically don’t find medium-sized eggs in the grocery store, so how would you suggest I adjust the time (and any ingredient amounts) for large or extra-large eggs? Mahalo! (Thank you.)
Hi Erika,
Thank you for finding my website!
I’m not sure how egg sizes are defined in your area, or if it’s a universal thing, but here in Japan, the definition of medium size is between 58g and 64g. As far as I know, Japanese medium eggs are a similar size to US large eggs so in theory, you don’t need to change the recipe. Hope this helps!
Yuto
Hi Yuto-san. Your Onsen Tamago looks amazing. Thanks for sharing this recipe. Question: Instead of bringing the water to boil and adding cold water to lower the temperature, can I just bring the water to 80 degrees C with a thermometer?
Hi Julie,
Thank you for checking out this recipe! And yes, if you have a thermometer, you can just heat the water to 80! 🙂
Yuto
Thank you!
Hello Yuto,
Thanks for sharing this recipe. When I placed the eggs from the fridge directly to the 80C water, some of the eggs cracked. Why is that and why only some of the eggs cracked but not the others?
Hi Dennjs,
Thank you for sharing your experience and question!
There are a few reasons why some eggs might crack while cooking, but the most common is that the egg hits the bottom of the pot hard, creating a small crack that then expands. So possibly, the cracked eggs might have been hit harder than the others. To avoid this, I try not to drop the eggs directly into the water and instead, I put them on a skimmer one at a time and slowly lower them into the pot.
Another possibility is how fresh the eggs are. Extremely fresh eggs tend to have more carbon dioxide gas, which tries to escape when heated. The pressure from this gas can cause the shell to crack.
Additionally, there are individual differences in eggshell hardness. For example, it depends on the age of the hen (younger hens tend to lay eggs with harder shells), the nutrients in the hen’s feed, and the time of year the egg was laid (eggs laid in summer tend to have thinner shells).
I can’t say for sure what’s causing it in your case, but I hope this info helps. If you have further questions, ask me here anytime! 🙂
Yuto
Thank you so much for your reply. I actually used a ladle to place the eggs one at a time. Anyways, I’ll try to be more careful next time.
I followed the instructions for this recipe. Yet somehow the eggs were still undercooked. I guess my question is what is the key temperature for cooking the eggs for this recipe? I would like to try this again, but will use a thermometer to make sure I have the temp right.
Thank you once again and for sharing all these wonderful recipes!
May I ask how undercooked the eggs were? Were they slightly undercooked or almost raw?
The crucial point in this recipe is getting a water temperature of 80°C (176°F) after adding 300 ml of chilled water to 1500 ml of boiling water in a pot. However, if the eggs still come out underdone, you can consider leaving them in the pot for an additional 1-2 minutes. This adjustment may be necessary due to variations in climate or the pot’s heat retention capabilities.
If you have any further questions, please don’t hesitate to ask. I’m here to help!
Yuto