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.


