📝 About This Recipe
Literally translating to 'hot spring egg,' Onsen Tamago is a Japanese culinary marvel where the egg is slow-cooked at a precise temperature to achieve a custard-like yolk and whites that are incredibly soft and delicate. Traditionally prepared in the geothermal waters of Japan's volcanic springs, this dish offers a unique texture that is neither poached nor hard-boiled, but rather a velvety, melt-in-your-mouth experience. Served in a chilled, umami-rich dashi broth, it is a sophisticated testament to the beauty of simple, high-quality ingredients.
🥗 Ingredients
The Eggs
- 4 pieces Large Eggs (must be at room temperature for accurate timing)
The Dashi Sauce
- 1/2 cup Water
- 1 small piece Kombu (Dried Kelp) (about 2x2 inches)
- 1/4 cup Katsuobushi (Bonito Flakes) (tightly packed)
- 1 tablespoon Usukuchi (Light Soy Sauce) (provides salt without darkening the broth)
- 1 tablespoon Mirin (Japanese sweet rice wine)
- 1/2 teaspoon Sugar (to balance the saltiness)
Garnish & Finishing
- 1 stalk Scallions (finely sliced into rounds)
- 1 teaspoon Toasted Sesame Seeds (white or black)
- 1 teaspoon Wasabi Paste (for a tiny kick of heat)
- 1 pinch Shichimi Togarashi (Japanese seven-spice powder)
- 1 pinch Katsuobushi (extra for topping)
Temperature Control
- 1 cup Cold Tap Water (to stabilize the boiling water temperature)
- 4-5 cups Boiling Water (enough to fully submerge the eggs)
👨🍳 Instructions
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1
Take your eggs out of the refrigerator at least 30 minutes before cooking. They must be at room temperature to ensure the whites and yolks set correctly within the designated timeframe.
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2
Prepare the dashi sauce by combining 1/2 cup water and the kombu in a small saucepan. Bring to a gentle simmer over medium heat, then remove the kombu just before the water boils.
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3
Add the katsuobushi (bonito flakes) to the saucepan. Let it boil for 30 seconds, then turn off the heat and let the flakes steep for 2 minutes until they sink to the bottom.
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4
Strain the liquid through a fine-mesh sieve or cheesecloth into a clean bowl. Stir in the light soy sauce, mirin, and sugar until the sugar is completely dissolved. Set aside to cool, then refrigerate until chilled.
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5
In a heavy-bottomed pot (like a Dutch oven which retains heat well), bring 1 liter (about 4-5 cups) of water to a rolling boil.
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6
Once boiling, remove the pot from the heat source and immediately add 1 cup (240ml) of room-temperature tap water. This brings the temperature down to approximately 165-175°F (75-80°C), the 'sweet spot' for Onsen Tamago.
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7
Carefully lower the room-temperature eggs into the water using a slotted spoon. Ensure they are fully submerged and not touching each other too much.
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8
Cover the pot tightly with a lid. This traps the residual heat, allowing the eggs to cook slowly as the water temperature gradually drops.
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9
Let the eggs sit undisturbed for 17 to 20 minutes. 17 minutes will yield a runnier yolk, while 20 minutes will result in a jammy, custard-like center.
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10
While the eggs cook, prepare an ice bath in a medium bowl. When the timer goes off, use a slotted spoon to transfer the eggs immediately to the ice bath for 3-5 minutes to stop the cooking process.
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11
To serve, gently crack the eggshell just as you would a raw egg. Carefully slide the contents into a small, shallow individual serving bowl.
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12
Pour 2 tablespoons of the chilled dashi sauce around the egg (not directly over the yolk to maintain its beauty).
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13
Garnish with a small mound of sliced scallions, a tiny dab of wasabi on the side, a sprinkle of toasted sesame seeds, and a pinch of shichimi togarashi for color and warmth.
💡 Chef's Tips
Always use the freshest eggs possible for the best flavor and a more cohesive white. If you have a sous-vide machine, set it to 145°F (63°C) and cook the eggs for 45 minutes for a perfect, foolproof result. Avoid using extra-large eggs with this specific timing; stick to standard 'large' eggs to ensure the heat penetrates the center correctly. If the egg white is too watery when you crack it, you can gently drain the very thin 'outer' white before placing the egg in the sauce. Never boil the eggs directly; the goal is to keep the temperature below the point where the whites become rubbery.
🍽️ Serving Suggestions
Serve as a traditional Japanese breakfast alongside a bowl of steamed white rice and grilled salted salmon. Place the egg atop a bowl of hot Gyudon (beef bowl) or Kitsune Udon for a luxurious, creamy addition. Pair with a chilled glass of dry Junmai Sake to complement the umami of the dashi. Use it as a dipping sauce for Sukiyaki, where the silken yolk coats the hot slices of beef. Enjoy as a light appetizer (Zensai) before a multi-course Japanese dinner.