Defrost puff pastry.
Wipe the mushrooms with a damp cloth and chop. Peel and chop the onions. Heat half the butter or margarine in a pan and sauté the onions until transparent. Add the mushrooms and sauté until most of the liquid has evaporated.
Remove from the heat and stir in the hanepoot wine, cream and a little of the parsley. Heat until all the moisture has evaporated. Chill.
Season the beef fillet with salt and pepper and fry in the remaining butter until the outside is nicely browned.
On a lightly floured, cold surface roll out the pastry into a 40 x 35 cm rectangle. Trim the edges and cut the remaining bits of dough into decorative shapes. Spoon a quarter of the mushroom mixture onto the rolled pastry and place the beef fillet on top. Spoon the remaining mushroom mixture over the meat and fold on sides of the dough over the meat. Brush the edges with egg white and press firmly together.
Place the dough-wrapped fillet of beef on a greased baking sheet with the folded edge facing down. Place the decorative dough shapes on top, securing them with egg white. Chill for about 30 minutes. Brush with egg yolk and bake for 30 to 35 minutes until the crust is golden brown.
Recipe reprinted with permission of You