Cut beef into thin strips. Best to slice the meat against the grain (reference video). Cut the onion into thin strips as well

Make the marinade: Mix soy sauce, minced garlic, sugar, mirin, and black pepper thoroughly.

Place meat strips into marinade. Let it soak for 15-30 minutes. (30 minutes is best, but 15 is ok if you are in a rush :) )

Cut the spring onion stalk into finger-length pieces. Collect the white stalks - and split each piece down the middle. Stack each layer on top of each other. Then make very thin Julienne slices. Repeat for the green stalk pieces as well.

Fill a mixing bowl with very cold water. Put the spring onion slices in and let it soak for 15 minutes.

Now let make sauce: Mix gochugaru, soy sauce, sugar, vinegar and sesame oil thoroughly together. 

After 15 minutes, drain the spring onion slices and let them drip-off excess water. Then place them in a mixing bowl. Put the sauce in and mix thoroughly. Salad is ready!

Put frying pan on high heat. Put some oil in.

Once oil is hot, place meat pieces in. Then add onion slices.

Cook meat to your preference. Turn off heat. Set aside

Take out a bowl. Put some rice on the bottom. Add a layer of spring onion slices. Then add beef strips and onions on top. Enjoy!