Soak a handful of bamboo skewers in water for at least 10 minutes.
While you preheat the grill or broiler, cut the steak into thin strips and thread a piece onto each skewer, winding back and forth in an S shape.
Grill or broil for 4-5 minutes, turning as necessary just until cooked through.
In a small bowl, stir together the ingredients for the peanut sauce. (If it’s tough to mix, 20 seconds in the microwave will soften the peanut butter enough for it to more easily blend.)
Serve the satay sprinkled with green onion, with peanut sauce for dipping.