1 Marinate the fillet in the white wine overnight.
Drain the fillet, reserving the marinade and dry it thoroughly.
2 Melt 50 g (2 oz) 1/4 cup) of the butter in a frying pan (skillet).
Add the bay leaf, thyme and chopped onion and saute gently for 5 minutes, or until the onion is transparent.
Add the mushrooms and seasoning.
Cover and cook over a low heat for 20 minutes.
Add the parsley and cook for 1 more minute before removing from the heat.
3 Preheat the oven to 200°C, 400°F; gas 6.
Using a sharp knife split the fillet lengthways and stuff it with the mushrooms.
Reserve any that are left over.
Tie the fillet with string and place it in a roasting tray.
Dot with the remaining butter and sprinkle it with the wine from the marinade.
Bake the meat in the oven for 50-60 minutes, basting frequently while it cooks.
4 Transfer the meat to a serving dish and surround it with any leftover mushrooms.
Serve with Potatoes in Green Sauce and a crisp mixed salad.