Clean the garlic, crush it with the flat side of a butcher knife, mince it, and set aside in a small bowl.
Wash the meat and cut into 1-inch beef cubes, then put aside.
Wash the lettuce, pat it dry with a paper towel, and lay the leaves on top of the plate on which you'll serve the dish. Next, cut the tomatoes, cucumbers, and onions into thin slices and place on top of the lettuce.
Chop green onions and set aside (do not add to the plate).
Heat 1 tablespoon of cooking oil in a large skillet over high heat, the add the minced garlic. Fry the garlic until golden, or approximately 30 seconds.
Add the beef to the skillet and stir it.
Place the soy sauce, fish sauce, MSG, sugar, and oyster sauce to the skillet, and mix everything together.
Continue to fry, stirring (or shaking the skillet) often. For medium rare, fry the beef for about 5 minutes, or 10 minutes if you prefer the meat well done. You should see the gravy appear at the bottom of the wok.
Place the meat over the "salad" on the serving plate, sprinkle the green onions on top, and serve with rice.