Onsen eggs are a thing of beauty. The Japanese make refular trips to the local hotsrpings found throughout the country, and they sometimes take eggs in with them to bathe. The water temp is usually right around 144 degrees farenheit, which happens to be the prefect temerature to cook a soft boiled egg. The fat in the yolk of the egg makes its coagulation temp higher at 149, than that of the pure protein white at 144. Sitting in the 144 degree bath slow cooks the white to solid, and leaves the yolk thickened and custardy but still viscous and runny. These eggs are hard to recreate without an immersion circulator (or hot springs) to hold the 144 temp steady, but you can find them regularly at local Portland spots Biwa in NE, and they are often on the menu at Ping in the Pearl.