Beef (thinly sliced)
Onion (sliced into strips)
Green Onion (Cut into 2″ pieces)
Soy Sauce
Sugar
Sesame Oil
Garlic Minced
Ginger Minced
Black Pepper

Mushrooms (sliced)

Once mixed, cover and put in fridge. I sealed mine in a ziploc bag with as little air as possible then put in the fridge over night. Grill it or cook in a very hot pan until just done.