Choose a sauté pan large enough to fit all the ossi buchi in one layer.
Heat the oil and brown the ossi buchi on both sides after lightly dusting them with flour. Remove them from the pan and reserve.
Add the butter to the pan and add the chopped vegetables with a pinch of salt to cook them gently without burning for a few minutes. When the vegetables are soft return the meat to the pan and add the wine. Cook gently until the moisture is almost completely dried out.
Add the hot stock, turn the heat down and cover with a tight lid. Cook gently for 1½ hours or until the meat is coming off the bone, turning them every 20 minutes or so. When turning the ossi buchi make sure that you lift them gently with a spatula so that they stay in one piece and the marrow is not lost.
When cooked place the ossi buchi on to the serving dish and keep them warm. Mix all the gremolata ingredients together and sprinkle on to the ossi buchi before serving.