Onsen Tamago literally means “hot spring eggs“ in Japanese. It refers to eggs that are slowly cooked in hot spring water to create silky egg whites and custard-like yolk. Here’s how you can make this delicious egg recipe at home.
In the past, I’ve shared some popular Japanese egg recipes on Just One Cookbook such as Omurice, Tamagoyaki, and Ramen Egg (Ajitsuke Tamago). Today I’ll add another popular dish to the egg recipe collection, and it’s Onsen Tamago (温泉卵).
What’s Onsen Tamago?
Onsen means hot springs, and tamago means eggs in Japanese. Why is the name “hot springs eggs”? Originally, eggs prepared this way were slow-cooked in Japan’s warm hot springs water.
What’s so special about these eggs? These eggs are perfectly poached inside its shell. While the whites are soft and silky, the yolk comes out firm but retains the color and creamy texture of an uncooked yolk. It’s basically the complete opposite of soft-boiled eggs, which are firm whites and soft egg yolk.
The Chemistry Behind Onsen Tamago
We can achieve this special texture because egg yolk and egg white solidify at different temperatures. Egg yolks solidify at 158°F (70°C) and egg whites solidify at 176°F (80°C). Therefore, if we maintain the cooking water at 149-154°F (65-68°C) for 30 minutes, we’ll get a perfect spherical poached egg, creamy and silky on the outside and firm on the inside.
This Recipe Works for Everyone
There are many ways to make the perfect onsen tamago, but this technique does not require a microwave, a thermometer, or any special cooking gadget.
Here are the highlights of this technique:
- Requires just a stove and pot (which I hope everyone has in their kitchen).
- Does NOT require a thermometer.
- Use refrigerated eggs. Some recipes require eggs to be “room temperature”, but the “room” temperature could be different depending on where you live.
- Not required to soak eggs in iced water after cooking, in case you don’t have ice cubes handy.
If you follow my recipe precisely, you should be able to achieve perfect onsen tamago as the final result. The only requirement is to use 4 large eggs. If you use different size eggs or reduce/increase the number of eggs, it will not work as the water temperature will change.
How Do you Enjoy Onsen Tamago?
You can enjoy onsen tamago with a dashi-based soy sauce (だし醤油) which is usually served as a part of Japanese breakfast. Also, you can place it on top of the steamed rice, splash some soy sauce over, mix, and enjoy; serve with gyudon, curry rice, soba noodle soup, and cold udon; or even mix with carbonara (my favorite!).
Now let’s get started! The best part about this recipe is you do not need to visit hot springs in Japan to enjoy these special eggs. Make the perfect onsen tamago right at home!
Disclaimer: Many people in the world including the Japanese consume uncooked eggs in their cuisine. However, according to the FDA, eggs should be cooked to 165 degrees °F (74 °C) in order to be considered safe. The perfect temperature for cooking onsen tamago is 149-154 degrees °F (65-68 °C), which is below the guideline. There is a risk of salmonella by consuming undercooked eggs.
Wish to learn more about Japanese cooking? Sign up for our free newsletter to receive cooking tips & recipe updates! And stay in touch with me on Facebook, Pinterest, YouTube, and Instagram.
Onsen Tamago (Japanese Slow-Cooked Eggs)
Video
Ingredients
- 4¼ cups water (measure 4¼ cups and remove 4 tsp, to be precise)
- 4 large eggs (50 g each w/o shell) (refrigerated)
- ¾ cup tap water (¾ cup + 4 tsp, to be precise; colder than room temperature)
For the Sauce
- ¼ cup dashi (Japanese soup stock) (use standard Awase Dashi, dashi packet or powder, or Vegan Dashi)
- ½ Tbsp mirin
- 1½ Tbsp soy sauce
- ⅓ cup katsuobushi (dried bonito flakes) (skip for vegetarian)
For the Garnish
- green onion/scallion
Instructions
- Gather all the ingredients. You will need a small heavy-bottomed saucepan (I use 1.5 QT); you will need to cover the eggs completely with the water.
- To the saucepan, add 4¼ cups water (measure 4¼ cups and remove 4 tsp, to be precise). Cover with a tight-fitting lid and bring it to a boil.
- Once boiling, remove the pot from the heat. Remove 4 large eggs (50 g each w/o shell) from the refrigerator. To the pot of hot water, add ¾ cup tap water that‘s colder than room temperature (¾ cup + 4 tsp, to be precise). Gently submerge the cold eggs in the hot water. Immediately cover and set the timer for 17 minutes.
- Meanwhile, make the sauce. Combine ¼ cup dashi (Japanese soup stock), ½ Tbsp mirin, and 1½ Tbsp soy sauce in a small saucepan and bring it to a boil. Add ⅓ cup katsuobushi (dried bonito flakes), turn off the heat, and let the katsuobushi sink to the bottom of the pan. After 30 seconds or so, strain through a sieve and set the sauce aside.
- Cut the green onion/scallion into thin slices and set aside.
- Once 17 minutes have passed, gently take the eggs out of the water and set them aside for 5 minutes.
To Serve
- Enjoy the Onsen Tamago either warm or at room temperature. Crack the egg into a small bowl, pour the dashi-based sauce into the bowl, and garnish with the sliced scallion as a part of a Japanese breakfast. Try the egg on top of steamed rice with a splash of soy sauce. It‘s also delicious over Gyudon, Chicken Curry Rice, Soba Noodle Soup, and Cold Tanuki Udon.
To Store
- You can keep the uncracked Onsen Tamago for 1–2 days in the refrigerator. To reheat, remove it from the refrigerator and bring it to room temperature. To warm it up further, place it in a bowl of 160ºF (70ºC) water for 10 minutes. Do not reheat higher than that; otherwise, the heat will cook the egg. Keep any leftover sauce in the refrigerator for 4–5 days.
For those of you who live at a high altitude (my home ~6,200ft), I tended to get the best results with 21 minutes
Hi O. Cornali, Thank you so much for trying Nami’s recipe and sharing your experience with us.
This helps other readers who live at high altitudes. Thank you very much!
I tried this recipe a few weeks ago and I did something wrong as my eggs were overcooked. Still tasty and they worked in the recipe I was making them for. I think either my tap water wasn’t cold enough or I took the eggs out of the fridge too soon.
I will be retrying the recipe again today as I have a craving for an egg over rice. I will be using a thermometer to make sure that the water temp is in the range listed.
I will update after I give it my second try. I hope it works, as I love onsen eggs!
Hi Victoria! Thank you so much for trying Nami’s recipe and sharing your experience with us.
We are sorry to hear that your first attempt did not go well. Hopefully, with a thermometer, it will be more accurate and work better for you.
Thank you for experimenting with Nami’s recipe!
It could also be an issue of a difference in altitude, in case you want to check that. Someone else said that for them, at a high altitude, 21 mins works the best.
Hi,
Would it be possible to have the quantities for one or two eggs only? I live alone, so I can’t eat four eggs in only one or two days…
Thanks a lot for your help.
Hello, Lilpea. Thank you so much for taking the time to read Nami’s post and try her recipe.
We only experimented with four eggs, but if you have a thermometer, try reducing the temperature of boiling water to 65~68C (149~154F). If you can maintain the temperature it should work with one or two eggs. We hope this helps!
I’m not sure what I did wrong with this recipe. I followed it very closely and watched the video as well and my eggs came out with a half clear egg white. I did use 4 eggs, although there are two in the photo. All I can think is maybe my tap water is too cold or I took the pan off the heat too quickly after it came to a boil or something. Any ideas what might have happened?
Hi, Teresa! Thank you for attempting Nami’s recipe!
We’re sorry to hear this recipe did not work out for you. It could be the altitude difference.
The boiling point temperature is lower at higher altitudes. It could also be the different temperatures of the tap water.
We hope that increasing the water temperature slightly next time will yield a better result.
Thank you for your reply. We are not at high altitude, but I wonder if it might be the tap water being too cold in winter. My basement is not heated, it only gets passive heating from the furnace being down there and it stays in the mid 50s F in the colder months in winter.
Did you ever test the temperature of the tap water used in the recipe? I’m just curious how my water compares. I will give it another try and let my tap water sit out for a little while first.
Hi Teresa! We didn’t check the tap water temperature, but the temperature after adding the tap water will be around 65~68C (149~154F).
We hope this helps!
I think you might want to check your 1 person serving adjustment to the recipe because I did as you said exactly. My egg wasn’t cooked 🙁
Hi Bec! Thank you for trying Nami’s recipe!
We’re sorry to hear you had trouble cooking the egg.
As Nami mentioned in this post, the cooking time is for 4 large eggs, and cooking only one egg may not work.
We hope this helps.
I followed the recipe exactly and it came out perfectly! Amazing how you guys figured out the logistics of the eggs, water, time and temp. This is definitely a super tasty way to make and eat eggs! Thank you!
Hi Jjanon! Aww. We are so happy to hear this recipe worked out well for you!
Thank you very much for trying Nami’s recipe and for your kind feedback!🥰
Followed this recipe to a T and these came out perfectly! Will be making on the reg now.
Hi Paige, We are so happy to hear Nami’s recipe worked very well for you!
Thank you very much for trying her recipe and for your kind feedback.😊
Wow!! These eggs have a wild texture I’ve never seen before. They were delicious on a beef bowl I made from your website. Much better texture than a typical soft boiled egg. Joe
Hi Joe! We are glad to hear you enjoyed Onsen Tamago! 😊
Thank you very much for trying Nami’s recipe and for your feedback!
Omg I’ve never made this before and this recipe was perfect and I can’t believe how yummy the eggs were with the sauce 😩 I’m so going to make it again!!
Hi Francesca! We are glad to hear you enjoyed Onsen Tamago!
Thank you very much for trying Nami’s recipe!
It really works, I didn’t believe it 😯. I accurately followed the recipe (1000 ml boiling water, 200 ml cold water etc.) but took only two eggs as I am single and they were really BIG with 65 grams with shell.
Made Onsen Benedict with it and it was sooooo good. Thank you for this ingenious recipe, will do it again soon.
Greetings from Switzerland
Brigitta
Hi Brigitta! We are so happy to hear this recipe worked very well for you!
Thank you very much for trying Nami’s recipe and for your kind feedback!☺️
17-mins on the stove cooked the eggs too much, I ended up with a hard boiled egg!
You weren’t supposed to leave them on the stove but let them heat slowly from the remaining heat in the water.
Thank you, Celeste!🙂
this is called not reading and following the instructions
Dear Nami, thanks so much for this recipe! how long and at which temperature should i cook the large eggs in a sous-vide to get the same consistency?
Hi Lena! Thank you very much for trying Nami’s recipe!
We have not tested this recipe with sous-vide before and are not sure of the actual temperature. However, the targeted temperature is 65~68C (149~154F) after you place the eggs in the pot. You can try that temperature for 17 minutes and see how it goes?
We hope this works!
THanks so much 🙂 i will do so and let you know about the result. regards from Switzerland!
Hi Lena! Yes, please! We would like to know how it goes!
Thank you for trying.😊
Have been enjoying your recipes immensely.
I am a Canadian born and raised in Japan and am at present still resident in the Tokyo area. Due to the fact that my Mother is a Canadian, I wasn’t given much instruction in Japanese cooking methods. What I learned was from friends and asking heaps of questions, so JOC site has very helpful in creating my confidence in the Japanese cooking methods. Many thanks for your thoughtful posts and recipes.
One question I have for you. When you speak of large eggs, you state that they should be 50g without the shell. How on earth are you supposed to know how much they weight when you are making things like onsen tamago or ramen tamago when these are dishes we cook with shell on.
In Japan there isn’t a standardized measurement for eggs like we get in the States or Canada, therefore your eggs come in various sizes in one case….
Hi Elizabeth, Thank you very much for your kind feedback!
Nami and JOC team are pleased to hear our posts and recipes help create your Japanese cooking confidence.😊
The standardized measurements for eggs are different in different countries, and our recipe shows both the egg’s US size and weight. Japan also uses the standardized measurement for eggs, and you should see a little colorful letter M, MS, L, LL in the egg cartons. The eggshell is usually 10% of the egg weight. So if you are in Japan, a Medium size 58g~64g “M” egg will be a good size for the recipe called for 50g egg without a shell.
We hope this helps!
I’m looking forward to trying this. One thing, I live at altitude (2500 meters) and water boils at around 91C. Should I put less cold water in or increase the amount of time the eggs sit in the water? A regular soft-boiled egg takes 3 1/2 minutes at this altitude.
Hi Mark, Thank you for trying this recipe! The reason to add the cold water to the boiling water is to lower the temperature so that Onsen Tamago will cook at 65~68C after you place the eggs in the pot. We don’t have experience cooking at an altitude of 2500 meters and unsure how the outcome will be. Maybe add less water?? In your case, we recommend using a thermometer to test it once. We hope this helps! Let us know how it goes!
Thanks. That makes sense.
Doing it now! I’M EXCITEEEEEEEEEEEEEEEEEEEEEEEEEEEEEDDDDDDDDDD!!! Will use homemade ponzu sauce since it’s on hand
Hi Meg, We hope it turned well and you enjoyed it! Thank you for trying this recipe!