P.F. Chang's Mongolian beef by Todd Wilbur's Top Secret Recipes is a good P.F. Chang copycat recipe. The recipe features fast-cooked beef with garlic and green onions, and the sauce mimics P.F. Chang's famous secret sauce.
To prepare the sauce for the Mongolian beef recipe, place 2 tablespoons of vegetable oil in a saucepan over medium-low heat, and toss in 1 tablespoon chopped garlic and 1/2 teaspoon minced ginger. Before the garlic burns, add 1/2 cup water and 1/2 cup soy sauce. Pour in 3/4 cup dark brown sugar before raising the heat to medium-high and boiling until thickened, around two or three minutes. Turn off the heat, and prepare 1 pound of flank steak by cutting it against the grain at an angle into 1/4-inch thick slices.
Place 1/4 cup cornstarch in a bowl, and lightly dust the slices of beef before setting them aside for at least 10 minutes to let the cornstarch set. Heat 1 cup vegetable oil in a wok or heavy skillet over medium heat until hot but not smoking, and saute beef until the edges begin to brown or around two minutes. Move the beef onto paper towels using a slotted spoon, and remove the oil from the wok. Place the meat back in the wok and continue to saute for one minute before adding the sauce, cooking an additional minute. Add two large green onions that have been sliced into 4-inch pieces, and cook for one more minute before turning off the heat and removing the prepared beef with a slotted spoon onto serving plates.