Onsen Tamago literally means ‘hot spring eggs’ in Japanese. It refers to eggs that were
originally prepared 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.

Onsen Tamago

INGREDIENTS

• 1000 ml water (about 4 cups)
• 200 ml tap water (little bit less than 1 cup) (needs to be colder than room temp)
• 4 large eggs (50 g each w/o shell) (refrigerated)

Sauce

• ¼ cup dashi (click to learn more about this soup stock) (for vegetarian use kombu dashi)
• ½ Tbsp mirin
• 1 ½ Tbsp soy sauce
• 3 g katsuobushi (dried bonito flakes) (skip for vegetarian)
• 1 green onion/scallion (for garnish)

INSTRUCTIONS

1. Gather all the ingredients. You will need a small heavy-bottomed saucepan (I use 1.5 QT); the water should cover the eggs with 1000 ml water completely.
   
2. Add 1000 ml water in the saucepan, cover with a tight-fitting lid, and bring it to a boil.
3. Once boiling, remove the pot from the heat. Take the eggs out from the refrigerator. Add 200 ml cold tap water and gently submerge the cold eggs in the hot water. Immediately cover and set the timer for 17 minutes.
4. If you like to enjoy onsen tamgo with the sauce, combine the dashi, mirin, and soy sauce in a small saucepan and bring it to a boil. Add katsuobushi and turn off the heat, let katsuobushi sink at the bottom of the pan. After 30 seconds or so, strain through the strainer and set the sauce aside. You can keep the sauce in refrigerator for 4-5 days.
5. Cut scallion into thinly slices and set aside.
6. Once 17 minutes have passed, take the eggs out gently and set aside for 5 minutes.
7. You can enjoy onsen tamago either cold or warm. Crack the egg and pour the sauce over, garnish with chopped scallion. 

To Store

1. You can keep the onsen tamago for 1-2 days in the refrigerator. To reheat, take out the onsen tamago from the fridge to room temperature. Place it in 160 ºF(70 ºC) water for 10 minutes to warm up. Do not reheat higher than that otherwise the egg will be cooked.

RECIPE NOTES

Equipment you will need:

• 5 qt saucepan with lid (make sure water will cover eggs)
• A ladle or mesh strainer

https://www.justonecookbook.com/onsen-tamago/