From simplyrecipes.com

Servings: 4
Prep time: 20 miutes
Cook time: 10 minutes
Difficulty: Easy

Marinade
1 tsp Soy Sauce
1 tsp Sherry
1/2 tsp Flour
1/8 tsp Pepper

Sauce
2 TBS Oyster Sauce
1 TBS Sherry
1 TBS Soy Sauce
1/4 cup Chicken Broth

3/4 lb sirloin, sliced thin in 1/2 inch long strips
2 cloves Garlic, pressed
1 TBS oil
1 TBS flour, to thicken sauce

Mix Marinade ingredients in a medium bowl, add beef and stir to coat.  Let sit for 10 minutes.

Heat wok or frying pan over high eat until a drop of water evaporates immediately.  Add oil.

Cook the meat for a minute or two, or until about half cooked and add garlic.  Continue cooking until beef is no longer pink, about another one or two minutes.

Add sauce and bring to a boil.  Add 1 TBS flour and stir until sauce thickens. 

Serve over rice.