Whitefish, such as brown croakers, flathead grey mullets, red seabreams, or olive flounders, is filleted into thin, 7–8 centimetres (2.8–3.1 in) long slices, seasoned with salt and ground black pepper, and pounded lightly with the back of the knife. Common fillings include ground beef, shiitake mushrooms, cucumber, crumbled tofu, chopped scallions, minced garlic, and toasted and ground sesame seeds. The inner surface of each fish slice is dusted with mung bean starch, the filling is placed on it and it is then folded in half and sealed. The edges of the dumplings are trimmed with kitchen scissors to create the half-moon shapes. The dumplings are then coated with mung bean starch, and cooked either in boiling water or in the steamer lined with Boston ivy leaves. Cooked dumplings are commonly served with a dipping sauce such as mustard or choganjang (soy sauce mixed with vinegar).