Marinate the beef in white wine overnight.
Melt the butter in a pan; add the brandy, bay leaf, thyme, and salt to taste.
Add the mushrooms and continue cooking.
Meanwhile drain the beef, putting aside the marinade.
Make an incision on the narrow side of the beef with a sharp knife.
Stuff with mushrooms, seal the two end with two pieces of meat from the inside of the fillet and tie the meat with strings to keep the stuffing inside.
Brown the fillet on all sides in the remaining butter or oil and baste it with some wine from the marinade then cover the pan.
Lower the heat and continue cooking for about 40 minutes or until cooked.
Serve the steak sliced and garnished with whole mushrooms sauteed in butter and sprigs of parsley.