In a mixing bowl, combine the gochujang paste, soy sauce, minced garlic, grated ginger, brown sugar, sesame oil, and beef broth. Stir until the mixture is smooth.
Place the sliced onion in the bottom of the slow cooker. Arrange the beef short ribs on top of the onion.
Pour the prepared sauce evenly over the ribs.
Cover and cook on low for 8 hours until the meat is very tender.
Serve the ribs and sauce over the steamed rice. Top each portion with sliced green onions and sesame seeds.