Trim the fat from the beef and season well with salt and black pepper. Melt the butter in a large frying pan, add the beef and seal on all sides, cooking for at least 10 minutes. Remove the beef from the pan and set aside. Add a little more butter to the pan and cook the onions and mushrooms until all the moisture has evaporated. Allow to cool. Preheat the oven to 200C/400F/gas 6. Roll out the pastry to a large rectangle and put on to a greased baking sheet. Spread the onion and mushroom mixture on to the centre of the pastry and put the beef on top of the mixture. Top the meat with a layer of pate, cheese and mustard. Brush the edges of the pastry with the beaten egg. Fold and seal the pastry, pressing down on the edges. Make some flowers and leaves with the leftover pastry to decorate, then brush the whole parcel with beaten egg. Bake in the centre of the oven for 20 minutes, then lower the heat to 180C/350F/gas 4 for a further 15 minutes until golden brown. For a normal beef wellington, simply omit the cheese and mustard. DISCLAIMER=A9 Copyright 1996 - SelecTV Cable Limited. All rights reserved. Carlton Food Network http://www.cfn.co.uk/ Posted to MM-Recipes Digest V4 #6 by "N.J.Smith" on Feb 10, 1999,