Step 1

Heat oil in a large frying pan over medium-high heat until smoking. Season the beef generously, add to the pan and sear, turning occasionally, for 6-8 minutes or until browned well all over. Transfer to a plate and pat dry with paper towel.

Step 2

Combine mustard and pâté in a bowl and brush all over fillet. Refrigerate.

Step 3

Meanwhile, pulse the mushrooms in batches in a food processor until finely chopped but still with a little texture. Using the same pan to sear the beef, heat butter over medium-high heat until foaming. Add the mushroom, season and cook, stirring occasionally, for 6-8 minutes or until the liquid evaporates and the mushroom begins to brown. Add the eschalot, thyme and garlic, and cook, stirring occasionally, for 2-3 minutes until softened, then deglaze the pan with brandy, scraping the base of the pan with a wooden spoon. Add the cream, bring to a simmer and reduce until the mixture has dried out. Check the seasoning, transfer to a bowl and chill in the refrigerator.

Step 4

Lay out a piece of baking paper on a work surface. Overlap the prosciutto in a rectangle on top, arranging it so it is the length of your beef fillet and wide enough to completely enclose the meat. Spread the mushroom mixture evenly over the prosciutto.

Step 5

Lay the beef on the closest edge of the prosciutto and roll it into a cylinder, using baking paper to help roll and enclose the beef (discard the baking paper). Wrap the beef cylinder tightly in plastic wrap and chill in the refrigerator for several hours. Remove the plastic wrap before cooking.

Step 6

Roll out the pastry on a lightly floured surface to a 30cm x 40cm rectangle.

Step 7

Lay the prosciutto-wrapped beef on one long side and brush the pastry edges with egg wash. Roll the beef and pastry into a snug cylinder and place seam-side down on a baking tray lined with baking paper. Pinch the pastry ends together to seal and trim off any excess. Brush thickly with egg wash, score in a decorative pattern with a small, sharp knife, and chill in the freezer for 30 minutes or the refrigerator for up to 24 hours.

Step 8

Preheat the oven to 210°C (fan-forced). Season the beef parcel with sea salt and bake for 35-40 minutes for medium-rare – the internal temperature will read 52°C on meat thermometer – and the pastry is golden brown. Set aside to rest for 15 minutes. Thickly slice to serve.