Slice the steak into small, thin pieces, approximately 3/4" (2 cm) square and 1/4" (5 mm) thick.
Combine all the ingredients for the marinade. Add the marinade to the meat and mix well. Marinate for at least 1 hour.
Soak the wooden skewers in water for at least 30 minutes. Thread the meat onto the skewers.
Preheat the grill. Grill the meat for 2-3 minutes on each side, or until it reaches your desired tenderness.
Garnish the lemongrass beef skewers with crushed peanuts and sautéed scallions before serving.
Notes
To make the sautéed scallion, heat up a non-stick pan with 2 teaspoons cooking oil. When the oil is hot, add in the 1/4 chopped scallions. Add salt to taste. Slightly sautéed for 1 minute.