Begin by preparing your bone-in beef short ribs. Trim any excess fat and pat them dry with paper towels. Season with salt and pepper.

In a large skillet over medium-high heat, heat oil and sear the ribs for 3–5 minutes per side until golden brown.

While searing, combine marinade ingredients in a bowl: soy sauce, hoisin sauce, mirin, brown sugar, garlic, ginger, and chili flakes.

Preheat your oven to 275°F (135°C). Transfer the seared ribs to a Dutch oven and pour the marinade over them. Add sliced onion and green onions, cover tightly, and slow-roast for 3–4 hours.

Remove ribs and let rest. Pour braising liquid into a skillet, simmer for 10–15 minutes until reduced to a glaze. Add cornstarch slurry if desired.

For caramelization, broil the ribs in the oven on high for 2–3 minutes until crispy.

Plate ribs over rice or noodles and drizzle with reduced glaze, garnishing with green onions or sesame seeds.