How to Make It
In a large enameled cast-iron casserole, heat the oil. Season the short ribs with salt and pepper. Working in 2 batches, sear over moderately high heat, turning, until browned all over, 5 minutes. Transfer to a plate.
Add the onion, garlic and ginger to the casserole and cook over moderate heat, stirring occasionally, until softened, about 5 minutes. Add the wine, bring to a boil and simmer until reduced by half, 3 minutes. Stir in the stock, soy sauce, mirin, brown sugar and the 1/2 cup of kimchi. Return the ribs to the casserole bone side up along with any accumulated juices. Bring to a boil, cover and reduce the heat to low. Simmer gently until the ribs are very tender, about 2 hours.
Transfer the ribs to a shallow serving bowl. Strain and degrease the sauce. Spoon some of the sauce over the ribs and garnish with scallions and sesame seeds. Serve with steamed rice and more kimchi.