This couldn’t be simpler.
Slice good quality beef, like sirloin steak (Dutch: lendelapje), in very thin slices and marinate in bulgogi sauce for half an hour. When pressed for time buy a jar of bulgogi sauce from an Asian food store.
These are the basic ingredients for the marinade:
1/2 cup soy sauce
1/3 cup sugar
3 tablespoons rice wine
2 tablespoons sesame oil
8 cloves garlic, minced
4 scallions, minced
2 tablespoons toasted sesame seeds
1/2 teaspoon black pepper, salt
When the BBQ is hot, place heavy tin foil on the grid and fry the marinated meat. At this point you can add mushrooms and sliced onion.
Grilling without tin foil is also possible, but the meat has to be sliced much thicker.
When the meat is done, take a leaf of lettuce (or any other large leavy vegetable), put some rice on it, the hot meat, a little fermented soy bean paste (sunchang ssamjang), slice of garlic, kimchi, and fold the lettuce leaf to form a small package. Eat.
The fermented soy bean paste provides for a great umami taste and can also be used as a dipping sauce for cucumber, raw onion or carrots.