Melt the butter with the oil in a large flameproof casserole with a tight-fitting lid large enough to hold the rabbit in a single layer. Season the rabbit pieces lightly with salt and add to the casserole with the onions, celery, chilli flakes and rosemary. Cover, reduce the heat to its lowest setting and cook for 1½ hours, turning the rabbit pieces every 30 minutes.
Remove the lid, increase the heat to high and boil for 15 minutes until most of the rabbit juices have evaporated. Add the lemon quarters and olives and stir well, then pour in the wine. Bring to the boil and boil for 2 minutes.
Add the stock and simmer, turning and basting the rabbit occasionally, for a further 10–12 minutes until the sauce is syrupy. Serve hot.