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.
Onsen Tamago Ingredients
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.