Dried fernbrake (gosari)
Dried young shoots of bracken fern that are soaked and boiled before cooking. They are chewy, slightly fibrous and earthy-nutty in flavour.
Caution: Bracken fern must never be eaten raw or merely soaked; after soaking it has to be boiled thoroughly and rinsed in several changes of water, because the plant contains harmful compounds that are largely removed only this way.
Gosari are the young, still-curled shoots of bracken fern, gathered in spring, blanched and dried. Dried, they are dark brown, hard and brittle. Only after long soaking and boiling do they turn tender, while keeping a pleasant chewy, fibrous texture rather like mushroom stems. The flavour is earthy and slightly nutty, and they take up seasoning, sesame oil and broth well. This makes them especially suited to braises, soups and seasoned vegetable side dishes. You can buy them dried in bags at Asian grocers, particularly Korean shops, sometimes also pre-soaked and vacuum-packed, or by mail order.
Substitute:
There is no truly good substitute, because the chewy, fibrous texture and earthy flavour are distinctive. In soups and braises, dried shiitake stems torn into strips come closest in bite, but they bring a much stronger mushroom flavour. Fresh ostrich fern fiddleheads are softer and greener in taste and only partly suitable.