Beef Wellington with Gorgonzola

STEP 1: MAKE THE ROUGH PUFF PASTRY (DAY BEFORE, OR 2 HOURS AHEAD)

Whisk the flour and fine sea salt together. Add the frozen butter cubes and toss to coat, leaving the cubes whole - rough puff depends on visible pieces of butter, not on rubbing them in. Stir the lemon juice into the ice water and add it a little at a time, cutting it in with a knife, until the dough just holds together; it should look shaggy and unpromising. Pat into a rectangle, wrap and chill 30 minutes. On a floured surface, roll to a long rectangle about 8 x 20 inches (20 x 50 cm), fold in three like a letter, turn 90 degrees, and repeat. Chill 30 minutes, do two more turns, chill again, then do a fifth and final turn. Wrap and refrigerate at least 1 hour. A good all-butter block puff is a legitimate substitute here and will not be the thing that fails.

STEP 2: FREEZE THE GORGONZOLA

Cut the gorgonzola into a long baton roughly 3/4 inch (2 cm) square and as close to the length of the fillet as the piece allows, joining two batons end to end if you need to. Wrap tightly and freeze for at least 1 hour; it can stay frozen overnight. Blue cheese at room temperature is effectively liquid at oven temperature and will soak the pastry from within before the crust has set.

STEP 3: SEAR AND CHILL THE BEEF - THE CRITICAL STEP

Season the fillet aggressively all over with the kosher salt and black pepper. Heat the oil in a heavy skillet until it shimmers and just begins to smoke. Sear the beef hard on every surface, including the ends, 60-90 seconds a side, until deeply browned. Do not roast it. Transfer directly to a wire rack and brush all over with the English mustard while the surface is still hot enough to take it. Let it cool on the rack, completely uncovered, for 30 minutes, then refrigerate it - still uncovered, still on the rack - for at least 2 hours and up to overnight. No foil, no wrap, no plate with a lid: trapped moisture and residual warmth are exactly what melt the butter out of the pastry and open the seams. A dry, cold, firm fillet is the foundation of everything that follows.

STEP 4: COOK THE DUXELLES UNTIL IT IS GENUINELY DRY

Pulse the mushrooms in a food processor to a coarse rubble, in batches, or chop very finely by hand. Melt the butter in a wide skillet over medium-high heat, add the shallots and cook 2 minutes, then add the mushrooms. They will release a startling amount of liquid. Keep the heat up and stir often. Cook until the pan is dry, the mixture has darkened, and it begins to squeak against the pan - 15-20 minutes, and rushing it here guarantees a soggy base. Add the garlic and thyme for the last minute, then the wine, and cook until the pan is dry again. Season with the kosher salt - lightly, because the Parma ham and gorgonzola both bring salt. Spread on a plate or tray and refrigerate until cold.

STEP 5: BUILD THE HAM LOG

Lay a large sheet of plastic wrap on the counter. Arrange the Parma ham on it in two overlapping rows, forming a rectangle wide enough to wrap right around the fillet and a little longer than it. Spread the cold duxelles evenly over the ham, leaving a bare inch (2.5 cm) along the far edge. Lay the chilled fillet across the near edge. Press the frozen gorgonzola baton into the duxelles along the top of the fillet, so the cheese is enclosed by mushroom on every side and never touches the pastry. Using the plastic wrap, roll the ham and duxelles tightly around the beef, then keep rolling the wrap itself into a tight cylinder and twist the ends like a sausage casing to compress it. Refrigerate 30 minutes, or freeze 15.

STEP 6: WRAP IN PASTRY

Roll the pastry on a lightly floured surface to about 14 x 12 inches (36 x 30 cm) and a scant 1/4 inch (5 mm) thick - thinner than feels safe, or the base will not bake. Optional belt and braces: lay the crepes over the center of the pastry as a second moisture barrier; they are invisible in the finished slice and they forgive a duxelles that was not quite dry enough. Beat the egg yolks with the heavy cream. Unwrap the ham log and set it on the pastry, brush the borders with the egg wash, bring the long sides up and over, overlapping by about an inch, and press to seal. Trim any thick overlap so there is no doubled slab of raw pastry underneath. Fold and seal the ends like a parcel, then roll the whole thing over so the seam sits underneath. It should measure around 10 inches (25 cm). Wrap in plastic and chill 30 minutes.

STEP 7: GLAZE AND SCORE

Heat the oven to 425°F (220°C) with the heavy baking sheet or baking steel on the middle shelf - give it a full 30 minutes to get properly hot. Unwrap the chilled Wellington onto a sheet of parchment. Brush all over with the remaining egg wash, chill 10 minutes, and brush a second time; two thin coats give a deeper color than one thick one and are far less likely to pool and burn. Score the top in a shallow diamond or chevron pattern with the back of a knife, cutting into the pastry but not through it. Cut two small vents in the top and scatter with the flaky sea salt.

STEP 8: BAKE - HOT START, PROBE FINISH

Slide the Wellington, on its parchment, straight onto the preheated sheet. Bake at 425°F (220°C) for 20 minutes, then reduce to 400°F (200°C) and bake a further 20-25 minutes. Start probing at the 35-minute mark: push the thermometer through a vent into the center of the beef and pull the Wellington at 120-125°F (49-52°C) for medium-rare after resting, or 130°F (54°C) for medium. Check the base as well as the beef: lift a corner with a spatula - it should be deep golden and firm, and a probe slid underneath should read above 200°F (93°C). If the top is dark before the base is done, tent it loosely and give it another 5-10 minutes on the hot sheet. Rest on a wire rack, uncovered, for 15 minutes before slicing; covering it now undoes the crust you spent three chills protecting.

STEP 9: CARVE AND SERVE

Use a long, sharp, serrated knife and a firm sawing motion rather than pressure, so the pastry does not compress. Slice into six thick rounds about 1 1/2 inches (4 cm) each. Serve with something sharp and green - watercress with a lemon dressing, or a red wine jus alongside. No sauce is needed on the plate; the gorgonzola is the sauce.