Slice the steak into thin strips. Put the sliced beef into a mixing bowl and add garlic paste, onion paste, soy sauce, gochujang, potato starch and baking soda.
Mix all the ingredients and beef together well. Make sure each slices of beef is coated well and marinate for at least 30 mins.
Cut the garlic, onion and spring onions into thin slices. Julienne the carrot.
Prepare the stir-fry sauce by mixing oyster sauce, soy sauce, gochujang, lemon juice, mirin, sugar and salt in a bowl.
Heat the pan into high heat, add the garlic slices and stir for few seconds.
Add the marinated beef, flatten and spread the beef in the pan. Let it cook the beef for ⅔ mins till the beef get nice color and turn side and cook for another ⅔ minutes.
Add the onions and carrots, stir for few seconds and add the chillies follow by stir-fry sauce.
Allow to simmer for a minute. Add spring onion slices. Mix all the ingredients well with the sauce until well combined.
Serve with a bowl of steamed rice. Sprinkle some tosted sesame seed on top.