The amount of ingredients for this depends on how many you are serving (obviously). A 1.4kg piece of beef was more than sufficient for 6, however making a wellington of this size is one hell of a battle so I advise you make two smaller ones of about 600g each
600g Beef Fillet
400g Chestnut Mushrooms
100g Cooked Chestnuts
6 Slices of Parma Ham
500g packet of Puff Pastry
2 egg yolks
Season the beef well with Salt and Pepper.
Heat a frying pan with plenty of oil until very very hot.
Sear the beef quickly on all sides to seal in the juices, do not cook the beef just colour.
Brush with plenty of mustard and leave to rest and cool on a plate.
Blend the mushrooms and chestnuts in a food processor.
Place them in a hot dry pan in order to remove all the water, this may take some time but is critical to the recipe. The mixture should be sticking together and no bubbling water should be seen.
Leave to cool
Roll out a long length of clingfilm and overlap the Parma ham in the middle.
Spoon out the mushrooms and spread over the ham, leave a bout an inch from all sides.
Place the beef in the centre.
Using the clingfilm roll up the ham, mushrooms and beef very tightly and twist the clingfilm at the ends as much as possible.
Leave to set for 20 minutes in the fridge.
Roll out the pastry and place on a long piece of clingfilm.
Place beef on the pastry and roll up, trim off the excess pastry and tighten up with the clingfilm, twisting tightly at the ends.
Leave to rest in the fridge for an hour. You can also leave it at this stage overnight in the fridge just remove a few hours before cooking so the beef can return to room temperature for cooking.
Brush the Wellington with egg wash and bake in a preheated oven (190C) for 45 minutes, depending on how you like your meat, (use a meat thermometer for a bit more guidance)