Beef Wellington

Pat the fillet bone-dry and season it hard all over with salt and pepper. Heat the oil in a heavy pan until shimmering and just smoking, then sear the fillet on every face — including the ends — for about 60-90 seconds each, until a deep brown crust forms. The goal is colour and flavour, not cooking the inside. Lift it out and let it rest and cool completely; searing a warm fillet then wrapping it would steam the pastry.

Blitz or finely chop the mushrooms to a coarse paste. Cook them with the shallots, garlic and thyme in a dry or barely-oiled pan over medium-high heat, stirring often. The mushrooms will release a flood of water — keep cooking, 15-20 minutes, until every drop has evaporated and the mass darkens into a thick, dry, intensely savoury duxelles. Season and cool completely. Any residual moisture here will turn the pastry to paste.

Lay overlapping sheets of prosciutto on a large sheet of cling film to form a rectangle big enough to enclose the fillet. Spread the cooled duxelles evenly over the ham. Brush the cooled fillet all over with mustard, lay it along the edge of the duxelles, and use the cling film to roll the ham and mushroom tightly around the beef into a firm, even log. Twist the ends like a cracker to compress it, then chill for at least 20 minutes to set the shape.

Roll the chilled puff pastry into a rectangle large enough to enclose the log with a little overlap. Unwrap the chilled log onto the pastry, brush the pastry edges with egg yolk, and roll it up, sealing the seam underneath and pressing out any air. Trim and tuck the ends, sealing them with egg wash. Chill the parcel 15-20 minutes so the pastry stays cold, then brush all over with egg yolk, score the top lightly in a diagonal lattice, and sprinkle with flaky salt.

Bake on a preheated tray in a hot oven (200°C / 400°F) for 35-45 minutes, until the pastry is deep golden and crisp all over. Use a meat thermometer pushed into the centre of the beef: pull it at 50-52°C / 122-126°F for a rosy medium-rare, as it will carry over while resting. Rest the Wellington on a board for a full 10-15 minutes before slicing — this lets the juices settle so they don't flood out and sog the crust. Carve into thick slices with a serrated knife.