"The western influence can be seen in this dish. Note the use of olive oil."
Cut beef into 1/2 inch cubes, and marinate in fish sauce, sugar, half of the salt, 1 Tbls. of the vegetable oil, and 4 of the cloves of garlic, chopped. Allow to sit at least 30 minutes, then sprinkle with fresh ground pepper, the rest of the sale, and the olive oil. Set aside.
Heat the remaining vegetable oil in wok over high heat, and add the last garlic clove, and stir, then add meat and cook quickly. The beef should be seared on the outside and pink on the inside. Allow beef to cool slightly. Combine the watercress and the onions on a platter and spoon beef over and lightly toss. Serve immediately.
I guarantee you, this is a sure-fire winner if you have a hot date coming over for dinner. Spouses may be "hot dates."