Cut Meat: Cut the flank steak into ¼” thick strips against the grain. OPTIONAL STEP: To tenderize the meat a little more, gently pound out the strips with a meat mallet or the back of a small pan. Put the strips in a large zip lock baggie.
Marinade: In a small bowl, whisk together the brown sugar, soy sauce, rice vinegar, sesame oil, ginger and red pepper flakes. Pour the mixture into the zip lock baggie with the flank steak strips. Make sure all the strips get coated with the marinade and put the sealed baggie in the fridge to marinate for 1-24 hours (overnight is ideal!).
Make Peanut Sauce: Put all peanut sauce ingredients in a small/medium bowl. Whisk until well combined and the sauce is smooth. Serve immediately or store in a sealed container in the fridge until needed (see note 1).
Soak Skewers: If you are using wood skewers, soak them in water for at least 30 minutes to keep them from burning on the grill.
Prep Veggies: Cut the head of cabbage into wedges (at least 8). Cut the zucchini length wise into quarters. Season the veggies with a couple pinches of salt and coat with olive oil.
Prep Skewers: After the meat is done marinating, place the steak strips on the skewers in a repeating “S” shape. See note 2 and note 3.
Grill: Heat up the grill to 550 degrees. Grill the zucchini for 3-4 minutes on each side (7-8 minutes total). Grill the cabbage for 3 minutes on each side (6 minutes total). Grill the skewers for 2 minutes of each side (4-5 minutes total). Garnish the beef satay skewers with sesame seeds and fresh cilantro if desired. Enjoy!