Place steak cubes in a large mixing bowl, lightly season with salt and pepper and toss together. Set aside.
Place all marinade ingredients into a blender and blend until smooth. Reserve ⅓ cup of marinade for peanut sauce. Pour remaining marinade over beef and toss together until all beef cubes are completely covered. Allow mixture to marinate for at least 4 hours (ideally overnight).
Skewer 5 to 6 cubes of beef onto each bamboo skewer, until all beef has been used.
Place a grill pan over medium-high heat. Pour oil into pan and grill skewers for 2 minutes, on each side. Repeat until all skewers have been grilled. Top satay with chopped peanuts and green onions.
For spicy peanut sauce: Place all ingredients for peanut sauce into a blender and blend until smooth. (If sauce is too thick, blend some water into the sauce, ½ tablespoon at a time, until desired consistency has been achieved) Pour mixture into a small bowl or ramekin, top with chopped peanuts and serve as dipping sauce for satay.