Begin by trimming any excess fat from the bone-in beef short ribs, ensuring a better flavor and texture. Pat the ribs dry with paper towels, then season with salt and pepper.

Heat a splash of oil in a large skillet over medium-high heat. Once hot, add the seasoned short ribs and sear for 5–7 minutes until richly browned.

While the ribs are searing, combine the soy sauce, hoisin sauce, mirin, brown sugar, minced garlic, grated ginger, and optional chili flakes in a mixing bowl. Whisk until smooth.

Transfer the seared ribs to a Dutch oven and pour the marinade over them. Scatter the sliced onion on top. Cover and roast at 275–300°F for 3–4 hours.

Once tender, remove the ribs from the oven. Pour the braising liquid into a skillet and simmer over medium heat for 10–15 minutes until it thickens into a glossy glaze.

Preheat the broiler. Place the ribs on a baking sheet lined with parchment and brush with the thickened glaze. Broil for 2–3 minutes until caramelized.

Serve the ribs over a bed of jasmine rice or noodles. Drizzle with remaining glaze and garnish with green onions or sesame seeds.