Season the flour with salt and pepper and use to coat the beef. Melt the butter with the oil in a large, flameproof casserole and fry the beef in batches until deep brown. Drain with a slotted spoon while cooking the remainder.
Add the onions and celery and fry gently for 5 minutes. Return the beef to the pan and add the herbs, ale, stock and treacle. Bring just to the boil, then reduce the heat and cover with a lid. Bake in a preheated oven, 160°C (325°F), Gas Mark 3, for 1 hour.
Add the parsnips to the dish and return to the oven for a further 30 minutes or until the beef and parsnips are tender. Check the seasoning and serve.