beef tenderloin, top sirloin, New York, flank, or skirt steak
fresh minced ginger
peanut or other oil, divided
Black pepper, to taste
green onions, thinly sliced (optional)
Cooked rice, optional
cornstarch, dissolved in 3 Tbsp water
Slice the beef into 1/4-inch strips, across the grain. In a small bowl mix the cornstarch with the soy sauce, ginger, and 1 Tbsp of the oil. Add beef strips and toss to coat with marinade. Marinate for 20 minutes.
To make stir-fry sauce, in a bowl, whisk together the sherry, oyster sauce, sesame oil and dissolved cornstarch. Set aside.
Heat 1 Tbsp of the oil in a wok or large heavy skillet over medium-high heat and stir-fry the beef for 1 minute. Remove and set aside. Add the remaining 1 Tbsp oil to wok/skillet along with the mushrooms and garlic; stir-fry for 2 minutes. Return the beef to the wok/ skillet and add the stir-fry sauce; stir until sauce comes to a simmer and thickens, 30 seconds to 1 minute. Season with black pepper. Serve at once on warm plates, garnishing with green onions. Serve with cooked rice, as desired.