Method
Prep:40min  ›  Cook:1hr  ›  Ready in:1hr40min 

1. Preheat the oven to 190 C / Gas 5.
2. First prepare the duxelles mixture. Dice the mushrooms to tiny squares. Heat the butter in a pan, fry the onion and garlic until soft but not coloured. Add the mushrooms and cook, again without colouring for 5 minutes. Season, and add thyme and sage. Leave to cool.
3. Next make six pancakes. Combine the flour, eggs and milk and whisk well till smooth. Heat a small frying pan over medium high heat. Add a little of the butter. Once melted, add a ladleful of pancake batter and swirl until the bottom of the pan is covered. Cook till edges are dry and bubbles appear on the surface, then flip and cook until golden. Set pancakes aside and leave to cool.
4. Mix your mushroom duxelles mix with your chicken liver pate. Set aside.
5. Cover your work surface with plain flour, and roll out your pastry quite large, brush pastry with egg wash, and then layer the cooled pancakes over the top. Next add an even layer of duxelles and pate mixture on top of the pancakes.
6. Next, heat a frying pan with some oil over medium high heat. Season the beef fillet on all sides, then add to the pan and cook for a couple minutes on each side, searing the outside till browned. (Cooking the fillet at this stage till just browned will result in a medium rare Wellington. For a less pink centre, cook a little longer at this stage.)
7. The place your beef fillet on one end of the covered pastry. Fold over the sides and place seam-side down on a baking tray. Brush all over with egg wash.
8. Bake in the centre of the oven for 35 minutes. Let it rest whilst you prepare your sides, for a good 10 minutes before slicing. Enjoy!