Vietnamese "Shaking Beef" Salad

My mom is an excellent cook, which probably has a lot to do with the reason why I love to eat and why I love to cook. The only problem? She is so reluctant to teach me! I always guilt her by saying, "If you don't teach me, your grandchildren will never know what Vietnamese food is, they'll forget their roots and become obese on french fries and hamburgers!" This is not something she wants, especially since she has already seen some of my own Vietnamese culture lost (since I cannot speak the language), which makes her extremely sad. It's not exactly that she doesn't want me to know how to cook Vietnamese food, it's just hard for her to teach me when she doesn't know measurements or exact amounts. The way she knows how to cook is not by measuring cups but by feel, estimations, and memory. I just make sure to watch her cook as often as possible to learn her methods at the least. The following recipe is my mother's as best as I could reconstruct it. Don't worry, no flavor was lost in the translation...

My mom's Thit Bo Luc Lac or Vietnamese "Shaking Beef" Salad:

Yields: Enough for 4

Marinade:

1 lb. sirloin steak, cubed
1/2 teaspoon freshly cracked black pepper
1 1/2 teaspoons sugar
2 cloves garlic, minced
1 teaspoon fish sauce
1 tablespoon soy sauce

Dressing:
1 medium white onion, thinly sliced
1 1/2 teaspoon sugar
1 or 2 pinches salt
3 to 5 cracks black pepper
1 1/2 tablespoons rice vinegar
2 tablespoons water

4 cups of washed watercress

2 tbsn. canola oil

Directions:

Combine all ingredients for the dressing except the onion, mix well until the sugar is dissolved. Next, add the onion and allow to it to marinade in the dressing and soften.

For the marinade, combine all of the ingredients and then add the steak cubes. Toss to coat and allow to marinade at room temperature for a minimum of 20 minutes. Heat the canola oil in a large wok over high heat (if you do not have a wok, you can also use a large skillet). Add the beef in a single layer, allowing the meat to sear well, about 1 minute. Shake the wok around to sear all other sides, about 30 seconds on each side. Cook in batches if necessary (you don't want to overcrowd the pan and steam the meat). Total cooking time should be about 4 minutes until the meat is browned and medium rare. 

Once the beef is done, lay it on top of the watercress and drizzle with the onions and lots of dressing.

Note: It is best served alongside rice and sliced tomatoes.