
Prepare the beef. Cut your beef into thin slices, around ¼-inch thick. Place your beef in the freezer for about 30 minutes beforehand to make slicing easier.
Prepare the marinade. Combine all the marinade ingredients except the onions and green onions in a food processor or blender. Blend until you have an even mixture.
Marinate the beef. Place the sliced meat in a gallon-size zip-top bag or baking dish, then pour the marinade over it and add the onions and green onions. Cover or seal the bag, then place in the fridge to marinate. I like to let my meat marinate overnight, but you want to give it at least 2 hours, and you can go up to 24 hours.
Preheat the grill. Set your favorite grill up for high heat, around 425 degrees F. You can also make this on a griddle stir-fry style or in a heavy-bottom pot on the stovetop.
Cook the meat. Remove the beef and onions from the bag or bowl, then arrange them evenly in a grill basket, on your griddle, or in your pot. Cook the beef for 2-3 minutes per side until caramelized and cooked through.
Serve and enjoy. Transfer the beef from the grill to plates and serve with white rice, kimchi, or anything you like with Korean beef. Enjoy!