Spicy Beef Filet in Oyster Sauce

Stir together 1 teaspoon vegetable oil, 1 teaspoon oyster sauce, and 1/2 teaspoon cornstarch in a bowl. Add beef and toss to coat. Marinate in the refrigerator 30 to 45 minutes. Remove from the refrigerator 10 minutes before cooking.

Stir together water, 1 teaspoon cornstarch, 2 tablespoons oyster sauce, and pepper in a small bowl; set aside. Heat 1 tablespoon vegetable oil in a large skillet over high heat. Stir in onion, and cook until it beings to brown on the edges, about 1 minute. Add the beef, and continue cooking and stirring until the beef is just slightly pink, about 5 minutes. Pour in the sauce; cook and stir until the sauce has thickened and turned translucent, about 1 minute more.