Otherwise known as Bulgogi.
1 lb beef (boneless top loin or sirloin steak
1/4 c soy sauce
3 T sugar (leave out if "paleo-izing")
2 T sesame oil
1/4 t pepper
3 green onions, finely chopped
2 cloves garlic, chopped
Trim fat from beef. For ease in cutting, partially freeze beef about 1 1/2 hours before cutting. Cut beef diagonally across grain into 1/8 inch slices. Mix remaining ingredients in large bowl. Stir in beef until well coated. Cover and refrigerate minimum of 30 minutes, or overnight to completely flavor the meat. You can also pour it all into a freezer bag and freeze until you want to cook it.
Once it's marinated, stir fry in skillet or wok over medium heat until brown. In the picture you can see I added broccoli and cauliflower at the end and turned it into beef and broccoli :) It was really tasty that way too, or you can serve it as is, with kimchi and veggies on the side.