1 onion, chopped
200 g mushrooms, finely chopped
60 ml red wine
0 pinch of Salt and black pepper
2 tsp olive oil, to drizzle
6 x 125g fillet steaks (or 750g beef tenderloin, sliced into 6 even pieces)
2 sheets frozen puff pastry, thawed
6 slices of prosciutto or Parma ham
1 egg, lightly beaten
1 Melt the butter in a frying pan over a medium heat and cook the onion for five minutes. Stir in the mushrooms and cook for six minutes until browned. Stir in the red wine and bring to a boil, then simmer until it has almost evaporated. Season with salt and pepper. Remove from the pan and leave to cool.
2 Heat the oil in a heavy frying pan over a high heat. When hot, cook the steaks for 3-4 minutes, turning to brown on all sides. Transfer to a plate and leave to cool for 10 minutes.
3 Roll out the pastry sheets to make two squares, then slice each into three rectangles. Place one slice of prosciutto or Parma ham lengthways down the centre of each.
4 Top with the mushroom mixture and then a piece of beef. Fold in the sides, then fold over the long ends to enclose. Seal the edges.
5 Place the parcels, seam-side down, on a baking tray lined with parchment paper. Brush the top of the pastry with the beaten egg.
6 Preheat the oven to 200˚C/180˚C fan/gas mark 6 and bake for 15-20 minutes until the pastry is puffed and golden and a meat thermometer registers the beef at 52˚C for medium-rare. Leave to rest for five minutes before serving.
Freeze after step 5 and bake from frozen, adding an extra 20-25 minutes to the cooking time.