In a pot, mix together soy sauce, brown sugar, vinegar and sesame oil. Stir until brown sugar is no longer clumpy. Add in sliced ginger, chopped green onions, sesame seeds, and red pepper flakes.

Chop short ribs into 2 inch thick slices. Place short ribs in marinade, flat side down.

Simmer on medium to low heat for 2 hours, flipping over every 30 minutes to ensure the bottom doesn't become charred.

Remove short ribs from marinade and garnish with additional sesame seeds and chopped green onions.