Once places of legend and mystery- boiling sulphurous waters forced from deep within the earth, gouts of fiercesome steam and perhaps even home to ghosts and monsters- the onsen or spa towns that are dotted along Japan’s mountain ranges are now prime destinations for people to bathe and absorb the health giving properties of the mineral rich waters. Tourists flock to towns such as Beppu in Kyushu to take in the eight different ‘Hells’, buy concentrated mineral salts to infuse their own baths at home and to sample local foods cooked in the steam that issues from the hillside. These geothermally cooked foods are not just a recent invention for tourists however, locals have been utilising the naturally stable and constant temperature of the springs to prepare their food for centuries, the most popular use being for soft poached eggs, or onsen tamago. After dropping a basket of eggs into the pool of a hot spring, they could be left unattended for an hour or two while the owner went about their other duties (or simply had a relaxing bath) before returning to collect their cooked eggs- rich, soft, custardy yolks, suspended within the silkiest of egg whites, the type of slow cooked eggs that modern restaurant reviewers rave about.
These most delicate of eggs can be made just as well at home and with no need for a volcanic hot spring, slow cooking them for three quarters of an hour at a low temperature is all that’s needed to coax the eggs to lightly set perfection. Unlike boiled eggs which are forced into springy submission by the fierce heat of the water, onsen tamago are gently persuaded to gel into a mass that can barely hold itself together, collapsing lazily at the slightest touch of a chopstick into a creamy unctuous puddle. They’re a staple part of a Japanese breakfast, served on top of steaming hot rice or plunged in a pool of broth, but they also make an incredible topping for a bowl of ramen, cracked open over a plate of spicy karē-raisu or dipped into batter and fried as one of the most delectable tempura imaginable.
- 6 large eggs at room temperature
- Take the deepest, widest pan you own and fill it with cold water before putting it on the hob over a low flame- this recipe works better when you use the greatest volume of water possible, so a stock pot is ideal here. Place a wire steamer rack at the bottom of the pan, or screw up some tin foil and submerge that in the water with a few weights; this is to prevent your eggs from sitting in the hottest part of the water where they’ll overcook. Using an accurate thermometer monitor the temperature of the water as it slowly heats up, you’re looking for 62 or 63ºC, which incidentally is the temperature that the water leaves the ground in most Japanese hot springs.
- When the water reaches the ideal temperature turn off the heat, gently lower the eggs into their warm bath being careful not to crack their shells, place the lid on the pan and leave them to poach slowly for 45 minutes. During the cooking time you’ll need to regularly check the temperature of the water and adjust it accordingly- a gentle boost from the hob to add a bit more warmth or a little splash of cold water if you got carried away, just make sure the water stays within the 62-63ºC window. Alternatively if you have access to a water circulator, just set it to 63ºC and let it do its magic.
- Once the 45 minutes are up, fish the eggs out of the water with a ladle or mesh strainer and either use them immediately or plunge into iced water to halt the cooking process.
One of our favourite ways to serve onsen tamago is swimming in a pool of light, smoky dashi, with a few drops of burnt garlic oil; the look and aromas never fail to bring back memories of the violent, breathtaking landscapes surrounding Beppu.
- 6 warm onsen tamago
- 500ml dashi broth
- 1 tablespoon soy sauce
- 1 tablespoon sake
- 1 spring onion to serve
- aonori flakes to serve
- mayu (burnt garlic oil) to serve
- Gently heat the dashi, soy sauce and sake in a small pan until just simmering. Whilst waiting for the broth to warm up, carefully break the eggs into individual serving bowls, discarding any of the watery liquid that might detract from the smooth, delicate body of the eggs.
- When the seasoned dashi has come to temperature, take it off the heat and ladle enough into each bowl to just submerge the eggs. Drizzle a couple of drops of mayu over the surface of each bowl before scattering shreds of spring onion and a few flakes of aonori to finish.
Makes 6 soft boiled eggs.