Slice the steak into 1/4 inch thick long strips. Toss them in a bowl with garlic powder, Worcestershire sauce, soy sauce, and season with salt and pepper. Marinate for up to 4 hours.
Heat the oil in a non-stick pan over medium heat.
Skewer the sliced meat onto the wooden skewers and cook in the pan about 1 to 2 minutes on each side.
In the meantime: Heat a non-stick pan over medium-high heat. Add the soy sauce, peanut butter, red pepper flakes (if using), and half of the chicken broth. Bring to a simmer while stirring to incorporate all of the ingredients. Simmer until smooth and thickened. (Add a little more chicken broth at a time to achieve the proper consistency.)
Spoon the sauce over the steak skewers and garnish with scallions.