Heat the butter and vegetable oil in a frying pan. Once hot, add the chopped shallots and fry, stirring continually, for two minutes. Tip in the chopped mushrooms. Reduce the heat a little and continue stirring. Cook for about ten minutes until the mushrooms are softened and their liquid has evaporated. Stir in the cream and cook for a further two minutes, then remove from the heat and leave to cool
- Heat the oil in a frying pan over a high heat and season the loin all over with salt and pepper. Once the oil is smoking, add the mutton and fry on all sides until it is a caramel-brown colour. Place on a plate to cool.
- Place the crêpes onto the work surface, one layer thick, but overlapping – you need to create an area about twice the size of the loin and about 2.5cm longer at each end. Spread the mushroom duxelle over the crêpes.
- Lightly pat the loin with kitchen paper to remove any excess moisture, before placing the meat on top of the duxelle.
- Carefully roll the side closest to you over the meat, encasing it within the crêpes and mushrooms. The crêpes should cover the meat on all sides and trim off any excess.
- Place the wrapped loin onto a sheet of cling film and wrap up tightly into a cylinder. Set aside in the fridge for about half an hour or until completely cold.
- Roll out the pastry and brush with beaten egg yolk. Remove the cling film from the mutton and place the meat onto the middle of the pastry.
- Wrap the pastry up over the mutton. Lightly stretch one edge of the seam so that it is not too thick, then press down firmly to seal.
- You should be left with a tube that is open at either end. Use a rolling pin to lightly press the ends of the pastry together to seal them. Then, with a small knife, trim the edges on each side to form a triangle shape. Brush the triangle of pastry with a little egg and press it up against the side of the Wellington. Repeat with the other side before flipping over so that the Wellington is seam-side down.
- Place your Wellington onto a baking tray, brush with the remaining egg yolk and set aside in the fridge to chill for 5-10 minutes.
- Pre heat the oven to 180C/350F/Gas Mark 4
- Remove the Wellington from the fridge and score a pattern of your choice onto the top and bake for 25 minutes.
- Remove the Wellington from the oven and leave to rest for 10 minutes. This should give you a perfectly pink finish to your meat. If you prefer it more cooked, then leave in the oven for longer, but you must ensure the meat is well rested
Serve slices of the wellington with roast potatoes and cauliflower cheese.