In a blender, add the marinade ingredients and puree until smooth.
Place the beef in a medium mixing bowl. Add the marinade and let marinate for at least 30 minutes or up to overnight, covered in the fridge. Divide in half and freeze, if desired.
In a wok or large frying pan on medium high heat, add oil, then add some of the beef without overcrowding. Get a good sear on one side and flip over to sear the other side. Remove to a serving platter. Do this in multiple batches.
Once the beef is cooked, turn down the heat to medium and add the onions. Cook for 1-2 minutes and add to the beef.
Garnish with roasted sesame and chopped green onion.
Serve with Japanese rice and kimchi and/or other Korean sides, along with lettuce to wrap.