The Black Egg Tradition of Mount Hakone

Just two hours southwest of Tokyo is the Owakudani volcanic valley known as “the boiling valley”. This place was formed when Mount Hakone erupted 3000 years ago, you can still see some puffs of smoke as the volcano is still active.

Located at around 1000m high, the main sulfur mine is open to visitors and can be accessed by road or cable car which offers a stunning view over Lake Ashi and Ashi Mountain. And it is here that the famous Kuro-tamago or black eggs are found and visitors shop in the small shops in the area.

The legend of the black eggs dates back to the Heian era (794-1185) , when the well-known monk Kukai Kobo Daishi , founder of the Shingon (‘ true word ‘) school of Buddhism, visited the region, which at the time was known like Daijigoku or ‘ the great hell’ . It is said that he was saddened by the gloomy expressions on the faces of the inhabitants of this arid and desolate valley, so he said a prayer for the health and long life of the inhabitants. It is characterized by a Buddha statuette that he carved himself, which encouraged the consumption of eggs cooked in the boiling waters.

You can admire this statue that is located in a shrine called Owakudani Enmei Jizoson and it is customary to say a prayer for him and then eat a black egg, to increase life expectancy by seven years . These eggs can only be found in Owakudani, where they are cooked daily in the sulfur mine near the shrine. The valley, for its part, only changed its name in 1873, when the imperial couple visited the region. The name ‘big hell’ seemed a bit scary so it was changed to ‘ Boiling Valley ‘, as it is currently known.

Despite the spectacular and highly symbolic dimension of the color of black eggs, there is nothing magical about how they are produced. Chicken eggs with light-colored shells are immersed in the volcanic water for one hour at a temperature of 80°C. The iron contained in the sulfur penetrates the shell and begins to blacken it through a chemical reaction. After steaming at 100°C for another 15 minutes, the shell turns pitch black, while the interior remains white and yellow.

This “cooking” process is carried out by professionals, the so-called Mushitaka . The taste is similar to that of regular hard-boiled eggs, although stores suggest that it is made up of 20% more umami , giving the eggs a meaty, rich, and salty flavor. The stores have now been inspired by their flagship product for other products of the same color, although not because they have been cooked in volcanic waters, for example, ice cream, stuffed bread, sweets and more give them that black color very characteristic of black eggs with an especially impressive result!