1/4 cup soy sauce
1 tablespoon hoisin sauce
1 tablespoon sesame oil
2 teaspoons white sugar
1 tablespoon minced garlic
1 tablespoon red pepper flakes (optional)
1 pound beef flank steak, thinly sliced
1 tablespoon peanut oil
2 large green onions, thinly sliced
Whisk together the first 6 ingredients. Put marinade and beef in a large zip lock bag or in a large bowl and cover, and refrigerate 1 hour to overnight.
Heat the peanut oil in a wok or large, nonstick skillet over high heat.
Add the sliced green onions, and cook for 5 to 10 seconds before stirring in the beef. Cook and stir until the beef is no longer pink and is beginning to brown, about 5 minutes. Remove from heat. Serve with white or fried rice.