Preheat your oven to 300°F (150°C).

In a large Dutch oven or oven-safe pot, heat the vegetable oil over medium-high heat. Add the beef short ribs and sear on all sides until browned, about 3-4 minutes per side. Remove the ribs and set aside.

In the same pot, add the diced onion and sauté until translucent, about 5 minutes. Add the minced garlic and grated ginger, cooking for an additional minute until fragrant.

In a bowl, whisk together the soy sauce, brown sugar, rice vinegar, sesame oil, gochujang, and beef broth. Pour this mixture into the pot with the onions, garlic, and ginger.

Return the seared short ribs to the pot, ensuring they are submerged in the sauce. Bring to a simmer.

Cover the pot with a lid and transfer it to the preheated oven. Braise for 2.5 to 3 hours, or until the meat is tender and easily pulls away from the bone.

Once done, remove the pot from the oven and let it cool slightly. Skim off any excess fat from the surface of the sauce.

Serve the short ribs over steamed rice, drizzled with the braising sauce, and garnish with sliced green onions and sesame seeds.