Whisk together 3 of the chopped scallions, the garlic, sesame oil, soy sauce, fish sauce, brown sugar and gochujang. Place in a sealing plastic bag with the short ribs and allow to marinate for about 4 hours.
Transfer short ribs and sauce to a dutch oven-like pot. Add two cups of water and ginger. Cover and simmer until tender, about 2 hours.
Remove ribs and allow to rest. Strain solids out of sauce. Serve with sauce and chopped scallions.