Cut the beef into 18-millimeter cubes. Place the cubes in a large, resealable plastic bag and pour in the marinade. Press the air out of the bag and seal tightly. Turn the bag to distribute the marinade, place in a bowl, and refrigerate for 1 to 2 hours.
If using bamboo skewers, soak them in water for at least 30 minutes.
Remove the meat from the bag, reserving the marinade. Thread the meat onto skewers, leaving space between the cubes. Allow the meat to stand at room temperature for 15 to 30 minutes before grilling.
Prepare the grill for direct cooking over high heat (230° to 290°C).
Prepare the grill for cooking over high heat (260°C).
Brush the cooking grates clean. Grill the skewers over direct high heat, with the lid closed, until cooked to your desired doneness, 3 to 5 minutes for medium rare, turning once. Remove from the grill.
Brush the cooking grates clean. Grill the skewers over high heat, with the lid closed, until cooked to your desired doneness, 3 to 5 minutes for medium rare, turning once. Remove from the grill.
Pour the reserved marinade into a small saucepan, bring to a boil over high heat on the stove, and boil for one full minute. Add the peanut butter, return to a boil, and whisk just until the sauce thickens. Serve warm with the beef skewers.
