Khmer hot beef salad

Sizzling sliced beef with sweet tangy vinaigrette sauce over crisp lettuce, tomato and cucumber is absolutely delicious. This authentic Khmer recipe takes more time to prepare but very little time to cook.
Ingredients :
½ or 1 lb Round or Sirloin beef, sliced thin
½ Teaspoon soy sauce
½ Teaspoon fish sauce
½ Teaspoon sugar
¼ Teaspoon salt
¼ Teaspoon black pepper
¼ Cup water
1 Tablespoon white vinegar
1 Tablespoon sugar
¼ Teaspoon salt
½ Tablespoon cornstarch
1 Small bunch Romain lettuce or ¼ head iceberg lettuce, chopped 2 inches in length
1 Cucumber, sliced
2 Tomatoes, thinly sliced
1 Vidalia onion (sweet onion),sliced
4 Cloves garlic, minced
3 Tablespoons vegetable oil
Procedures : In a large bowl, mix sliced beef with soy sauce, fish sauce, sugar, salt and black pepper, mix well and set a side.In a small bowl, mix water with vinegar, sugar, salt and cornstarch together, mix well and set a side. In a large plate or platter, arranges cucumber, tomatoes and ½ amount sliced onion, and put lettuce in the middle of plate, set a side. Heat up a skillet or wok in high temperature.When skillet is hot, add oil, garlic, onion and marinated beef, stirs and cook beef to your liking. Add vinaigrette sauce with beef, stirs till sauce thicken. Put hot beef on top crisp vegetables. Serve immediately with rice.