Trying to sum up this simple dish in words is difficult, and actually seems pointless. Onsen tamago, or onsen egg, simply has to be experienced. It’s so difficult to describe this slow poached egg, and yet so easy to create at home.
An onsen is a hot spring, plentiful in Japan which sits on the Ring of Fire. Often traditional hotels (ryokan) or public bathing facilities are built around onsen. In the context of this recipe, an onsen is a hot pool that can slowly cook eggs so that they are effectively soft boiled. We don’t have an onsen nearby (being a little far from the Ring of Fire); however, an immersion circulator (sous vide device), or diligent use of a digital thermometer, can achieve the same thing and produce great slow-poached onsen eggs.
If you stay in a ryokan in Japan and get up to a kaiseki style breakfast, one of the dishes presented to you is likely to be onsen tamago. The traditional onsen egg is topped with spring onions. These are replaced in this dish with truffle and sea grapes. This modification has two inspirations. Firstly, truffle goes so well with eggs. Scrambled eggs with truffle are one of those classic combinations. And then there is Tsuta, the first ramen restaurant to earn a Michelin star. Truffle oil is a key ingredient in their ramen.
If you cannot get summer truffle preserved in oil, or can’t justify the expense, rehydrate some shiitake mushrooms, dice finely and mix together with some truffle oil.
Sea grapes are beautiful and have a wonderful texture and taste. If you cannot buy sea grapes, revert to spring onions. They may not look as good or be as interesting to the bite, but they taste great!
Onsen Tamago (Poached egg in a dashi broth)
Ingredients
- 5 eggs
- 1 cup dashi
- 1/4 cup soy sauce buy a good quality one
- 1 Tbsp mirin
- 1 tsp sugar
- umibudo sea grapes
- 2 1/2 tsp finely chopped truffle slices from truffle slices preserved in oil – optional
- 2 1/2 tsp truffle oil
Instructions
- Bring the dashi, soy sauce, and mirin to a simmer and add the sugar.
- Stir until dissolved. Allow to cool, then keep in the refrigerator until ready.
- Have the eggs at room temperature.
Eggs – sous vide method
- Cook the eggs with an immersion circulator (sous vide) at 63 degC for 60 minutes.
- Transfer to an ice bath to stop the cooking.
Eggs – traditional method
- Cook the eggs in a large saucepan of water maintained at 75 degC for 11 minutes.
- Transfer to an ice bath to stop the cooking.
Plating
- Warm the eggs in 40 degC water for 2 minutes.
- Carefully crack the egg, draining off any watery egg white, then place the remaining white and yolk into a serving bowl.
- Pour 1/4 cup of the soy dashi broth around the egg.
- Top with 1/2 tsp finely diced truffle (if using) and a stem of sea grapes.
- Drizzle 1/2 tsp truffle infused oil over the dashi.
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