Tatties and herring is a traditional dish originating from Scotland. It's made with a combination of salt herring, potatoes, and salt. The fish is washed and sokaed in cold water overnight. The potaotes are boiled in salted water until just cooked.
The fish is simmered in another pot until the flesh is just soft, and it's then placed on heated plates. As soon as they're soft, the potatoes are removed from the water, drained, and returned to the heat for a few minutes before they're served whole, with their skin on, and accompanied by butter.