Although this is a classic French recipe it is best made with good English beef. The fillet of beef is the best cut and ask the butcher for a good even shape preferably from the thick end. If you want to cook for more than eight it is easier to use two separate fillets and cook them individually than one enormously long fillet.
If the skin is still on the fillet score it with a sharp knife.
Melt the butter in the small roasting tin on the floor of the roasting oven.Season the meat and then roll in the melted butter to coat all over.
Hang the roasting tin on the third set of runners from the top of the roasting oven and roast the meat for 20 minutes a little less for rare joints approximately 10 minutes more for a more welldone finished joint.
Remove the meat to a plate and allow to cool.Wash and slice the mushrooms toss them in the roasting pan and add the herbs.Put the pan on the floor of the roasting oven and cook the mushrooms until just cooked about 8 to 10 minutes.Remove and cool.Roll the pastry to 25mm longer than the fillet and three times as wide.