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. Place into the combi oven 140°C, 1hour and 30 minutes. Add the hot stock and cover with a tight lid, 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. Once cooked, place the ossi buchi on to the serving dish and keep them warm. Mix all the gremolata (lemon zest, thinly chopped garlic, thinly chopped parsley) ingredients together and sprinkle on to the ossi buchi before serving.