Directions

1. Freeze beef 20 minutes or until easy to slice. Trim fat; slice beef into strips 1/4-inch thick. Place beef in a resealable plastic bag set in a shallow baking dish. Set aside.
2. In a small bowl stir together soy sauce, brown sugar, vinegar, 1 tablespoon water, garlic, ginger and red pepper flakes. Pour over steak strips in bag; seal bag. Refrigerate 2 to 12 hours, turning bag occasionally.
3. Coat grill rack with nonstick cooking spray. Preheat grill to medium (300°F to 350°F). Remove steak strips from marinade; discard marinade. Thread onto skewers, folding each strip back and forth.?
4. Place skewers on grill. Grill 3 to 4 minutes per side or to desired doneness. Remove skewers from grill. If desired, place watercress on a serving platter, place skewers on watercress, and serve.