Put frying pan on medium-high heat. Place some oil in pan. When oil is hot, put spring onions in. Wait until they start to sizzle in the oil and get a slight brown on the edges.
Then put the mungbeansprouts into the frying pan. Place in the vinegar as well. Then add Baek's Soy Sauce. Give a quick and thorough mix - stirring frequently but not for too long!
Finish cooking when you see sprouts start turning slightly clear.