Begin by trimming excess fat from the bone-in beef short ribs, ensuring a clean surface for seasoning. Pat the ribs dry with paper towels, then generously season them with salt and pepper.

Heat a large skillet over medium-high heat, adding a splash of oil once hot. Carefully place the prepared short ribs in the skillet, browning them on all sides for about 4-5 minutes per side.

In a mixing bowl, combine soy sauce, hoisin sauce, mirin, brown sugar, minced garlic, grated ginger, and optional chili flakes. Whisk well until the sugar dissolves.

Transfer the seared short ribs to a Dutch oven and pour the marinade over them, ensuring they are well coated. Add the sliced onion and green onion pieces. Cover and place in an oven preheated to 275–300°F (135–150°C). Let roast for 3-4 hours.

Once fork-tender, remove the ribs and set aside. Pour the remaining liquid into a skillet over medium heat, simmering for 10-15 minutes until thickened. Optionally add a cornstarch slurry.

For added decadence, preheat your broiler. Place the ribs on a baking sheet and broil for 2-3 minutes until caramelized.

Plate the glazed ribs over steamed rice, noodles, or veggies. Drizzle the reduced sauce over the ribs and garnish with chopped green onions.