Oiseon is a traditional dish originating from South Korea. The dish is made with a combination of cucumbers, thinly sliced beef, salt, shiitake (brown oak) mushrooms, eggs, and a sauce consisting of soy sauce, water, sugar, scallions, garlic, sesame oil, and sesame seeds.
The cucumbers are slit and stuffed with a mixture of fried beef, mushrooms, egg yolks, and egg whites. They are then drizzled with the sweet and sour sauce. The dish is praised for its complex flavors and colors, and it's said that it stimulates the appetite, which is the reason why oiseon is traditionally served as an appetizer.